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arXiv:astro­ph/0312324
v2
7
Jul
2004
The Chandra Deep Field South:
Optical Spectroscopy I. 1
G. P. Szokoly 1;2 , J. Bergeron 3 , G. Hasinger 1;2 , I. Lehmann 1 . L. Kewley 4;5 , V. Mainieri 6 , M.
Nonino 7 , P. Rosati 6 , R. Giacconi 8 , R. Gilli 9 , R. Gilmozzi 6 , C. Norman 4 , M. Romaniello 6 E.
Schreier 8;10 , P. Tozzi 7 , J. X. Wang 4 , W. Zheng 4 and A. Zirm 4
szgyula@mpe.mpg.de
ABSTRACT
We present the results of our spectroscopic follow-up program of the X-ray
sources detected in the 942 ks exposure of the Chandra Deep Field South (CDFS).
288 possible counterparts were observed at the VLT with the FORS1/FORS2
spectrographs for 251 of the 349 Chandra sources (including three additional
faint X-ray sources). Spectra and R-band images are shown for all the observed
sources and R K colours are given for most of them. Spectroscopic redshifts were
obtained for 168 X-ray sources, of which 137 have both reliable optical identi-
cation and redshift estimate (including 16 external identications). The R< 24
observed sample comprises 161 X-ray objects (181 optical counterparts) and 126
of them have unambiguous spectroscopic identication. There are two spikes in
the redshift distribution, predominantly populated by type-2 AGN but also type-
1 AGN and X-ray normal galaxies: that at z = 0:734 is fairly narrow (in redshift
space) and comprises two clusters/groups of galaxies centered on extended X-ray
1 Max-Planck-Institut fur extraterrestrische Physik, Giessenbachstrae, Garching, D-85748 Germany
2 Astrophysikalisches Institute Potsdam, An der Sternwarte 16, Potsdam, D-14482, Germany
3 Institut d'Astrophysique de Paris, 98bis, bd Arago, 75014 Paris, France
4 The Johns Hopkins University, Department of Physics and Astronomy, Baltimore, MD 21218, USA
5 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
6 European Southern Observatory, Karl-Schwarzschild-Strasse 2, Garching, D-85748, Germany
7 Osservatorio Astronomico, Via G. Tiepolo 11, 34131 Trieste, Italy
8 Associated Universities, Inc. 1400 16th Stret, NW, Suite 730, Washington, DC 20036, USA
9 Osservatorio Astrosico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
10 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA

{ 2 {
sources, the second one at z = 0:674 is broader and should trace a sheet-like struc-
ture. The type-1 and type-2 populations are clearly separated in X-ray/optical
diagnostics involving parameters sensitive to absorption/reddening: X-ray hard-
ness ratio (HR), optical/near-IR colour, soft X-ray ux and optical brightness.
Nevertheless, these two populations cover similar ranges of hard X-ray luminosity
and absolute K magnitude, thus trace similar levels of gravitational accretion.
Consequently, we introduce a new classication based solely on X-ray properties,
HR and X-ray luminosity, consistent with the unied AGN model. This X-
ray classication uncovers a large fraction of optically obscured, X-ray luminous
AGNs missed by the classical optical classication. We nd a similar number
of X-ray type-1 and type-2 QSOs (LX (0.5-10 keV)> 10 44 erg s 1 ) at z > 2 (13
sources with unambiguous spectroscopic identication); most X-ray type-1 QSOs
are bright, R. 24, whereas most X-ray type-2 QSOs have R& 24 which may ex-
plain the dierence with the CDFN results as few spectroscopic redshifts were
obtained for R> 24 CDFN X-ray counterparts. There are X-ray type-1 QSOs
down to z  0:5, but a strong decrease at z < 2 in the fraction of luminous X-ray
type-2 QSOs may indicate a cosmic evolution of the X-ray luminosity function
of the type-2 population. An X-ray spectral analysis is required to conrm this
possible evolution. The red colour of most X-ray type-2 AGN could be due to
dust associated with the X-ray absorbing material and/or a substantial contri-
bution of the host galaxy light. The latter can also be important for some redder
X-ray type-1 AGN. There is a large population of EROs (R K> 5) as X-ray
counterparts and their fraction strongly increases with decreasing optical ux,
up to 25% for the R 24 sample. They cover the whole range of X-ray hardness
ratios, comprise objects of various classes (in particular a high fraction of z & 1
X-ray absorbed AGNs, but also elliptical and starburst galaxies) and more than
half of them should be fairly bright X-ray sources (LX (0.5-10 keV)> 10 42 erg s 1 ).
Photometric redshifts will be necessary to derive the properties and evolution of
the X-ray selected EROs.
Subject headings: surveys | galaxies: active | cosmology: observations |
quasars: general, evolution | X-rays: galaxies: clusters | techniques: spectro-
scopic
1 Based on observations collected at the European Southern Observatory, Chile (ESO N o 66.A-0270(A)
and 67.A-0418(A)).

{ 3 {
1. INTRODUCTION
Deep X-ray surveys indicate that the cosmic X-ray background (XRB) is largely due
to accretion onto supermassive black holes, integrated over cosmic time. In the soft (0.5{2
keV) band more than 90% of the XRB ux has been resolved using 1.4 Msec observations
with ROSAT (Hasinger et al. 1998) and 1-2 Msec Chandra observations (Brandt et al.
2001a; Rosati et al. 2002; Brandt et al. 2002) and 100 ksec observations with XMM-
Newton (Hasinger et al. 2001). In the harder (2-10 keV) band a similar fraction of the
background has been resolved with the above Chandra and XMM-Newton surveys, reaching
source densities of about 4000 deg 2 . Surveys in the very hard (5-10 keV) band have been
pioneered using BeppoSAX, which resolved about 30% of the XRB (Fiore et al. 1999).
XMM-Newton and Chandra have now also resolved the majority (60-70%) of the very hard
X-ray background.
Optical follow-up programs with 8-10m telescopes have been completed for the ROSAT
deep surveys and nd predominantly Active Galactic Nuclei (AGN) as counterparts of the
faint X-ray source population (Schmidt et al. 1998; Zamorani et al. 1999; Lehmann et
al. 2001), mainly X-ray and optically unobscured AGN (type-1 Seyferts and QSOs) and a
smaller fraction of obscured AGN (type-2 Seyferts). The X-ray observations have so far been
about consistent with population synthesis models based on unied AGN schemes (Comastri
et al. 1995; Gilli et al. 2001), which explain the hard spectrum of the X-ray background by
a mixture of X-ray absorbed and unabsorbed AGN, folded with the corresponding luminosity
function and its cosmological evolution. According to these models, most AGN spectra are
heavily absorbed and about 80% of the light produced by accretion will be absorbed by
gas and dust which may reside in nuclear starburst regions that feed the AGN (Fabian et
al. 1998). However, these models are far from unique and contain a number of often
overlooked assumptions, so their predictive power remains limited until complete samples
of spectroscopically classied hard X-ray sources are available. In particular, they require
a substantial contribution of high-luminosity absorbed X-ray sources (type-2 QSOs), which
so far have only scarcely been detected. The cosmic history of obscuration and its potential
dependence on intrinsic source luminosity remain completely unknown. Gilli et al. (2001)
e.g. assumed a strong evolution of the absorbed/obscured fraction (ratio of type-2/type-1
AGN) from 4:1 in the local universe to much larger fractions (10:1) at high redshifts (see also
Fabian et al. 1998). The gas-to-dust ratio in high-redshift, high-luminosity AGN could be
completely dierent from the usually assumed Galactic value due to sputtering of the dust
particles in the strong radiation eld (Granato et al. 1997). There could thus be objects
which are heavily absorbed at X-rays and unobscured at optical wavelengths.
After having understood the basic contributions to the X-ray background, the general

{ 4 {
interest is now focussing on understanding the physical nature of these sources, the cosmolog-
ical evolution of their properties, and their role in models of galaxy evolution. We know that
basically every galaxy with a spheroidal component in the local universe has a supermassive
black hole in its centre (Gebhardt et al. 2000). The luminosity function of X-ray selected
AGN shows strong cosmological density evolution at redshifts up to 2, which goes hand in
hand with the cosmic star formation history (Miyaji et al. 2000). At the redshift peak
of optically selected QSOs, around z=2.5, the AGN space density is several hundred times
higher than locally, which is in line with the assumption that most galaxies have been active
in the past and that the feeding of their black holes is re ected in the X-ray background.
While the comoving space density of optically and radio-selected QSOs has been shown to
decline signicantly beyond a redshift of 2.5 (Schmidt et al. 1997; Fan et al. 2001; Shaver
et al. 1996), the statistical quality of X-ray selected high-redshift AGN samples still needs
to be improved (Miyaji et al. 2000). The new Chandra and XMM-Newton surveys are now
providing strong additional constraints.
Optical identications of the deepest Chandra and XMM-Newton elds are still in
progress, however, a mixture of obscured and unobscured AGN with an increasing fraction of
obscuration at lower ux levels seems to be the dominant population in these samples (Fiore
et al. 2000; Barger et al. 2001a; Tozzi et al. 2001; Rosati et al. 2002; Stern et al. 2002).
First examples of the long-sought class of high-redshift, radio-quiet, high-luminosity, heavily
obscured active galactic nuclei (type-2 QSO) have also been detected in deep Chandra elds
(Norman et al. 2002; Stern et al. 2002) and in the XMM-Newton deep survey in the
Lockman Hole eld (Hasinger 2002).
In this paper we report on our optical identication work in the Chandra Deep Field
South, which, thanks to the eôciency of the VLT, has progressed to the faintest magnitudes
among the deepest X-ray surveys.
2. THE CHANDRA DEEP FIELD SOUTH (CDFS)
The Chandra X-ray Observatory has performed deep X-ray surveys in a number of elds
with ever increasing exposure times (Mushotzky et al. 2000; Hornschemeier et al. 2000;
Giacconi et al. 2001; Tozzi et al. 2001; Brandt et al. 2001a) and has completed a 1 Msec
exposure in the Chandra Deep Field South, CDFS (Giacconi et al. 2002; Rosati et al. 2002)
and a 2 Msec exposure in the Hubble Deep Field North, HDF-N (Brandt et al. 2002). The
Megasecond dataset of the CDFS is the result of the coaddition of 11 individual Chandra
ACIS-I exposures with aimpoints only a few arcsec from each other. The nominal aim point
of the CDFS is  = 3 : 32 : 28:0, ô = 27 : 48 : 30 (J2000). This eld was selected in a

{ 5 {
patch of the southern sky characterized by a low galactic neutral hydrogen column density,
NH = 8  10 19 cm 2 , and a lack of bright stars (Rosati et al. 2002).
3. OPTICAL IDENTIFICATIONS IN THE CDFS
Our primary optical imaging was obtained using the FORS1 camera on the ANTU
(UT-1 at VLT) telescope. The R band mosaics cover 360 arcmin 2 to depths between 26
and 26.7 (Vega magnitudes). This data does not cover the full CDFS area and must be
supplemented with other observations (see Figure 14). The ESO Imaging Survey (EIS) has
covered this eld to moderate depths (5  limiting AB magnitudes of 26.0, 25.7, 26.4, 25.4,
25.5 and 24.7 in U 0 , U, B, V, R and I, respectively) in several bands (Arnouts et al. 2001;
Vandame et al. 2001). The EIS data has been obtained using the Wide Field Imager (WFI)
on the ESO-MPG 2.2 meter telescope at La Silla. The positioning of the X-ray sources is
better than 0.5 00 (Giacconi et al. 2002) and we readily identify likely optical counterparts in
85% of the cases.
Figure 1 shows the classical correlation between the R-band magnitude and the soft X-
ray ux of the CDFS sources. The objects are marked according to their classication (see
below). By comparison with the deepest ROSAT survey in the Lockman Hole (Lehmann
et al. 2001), the Chandra data extend the previous ROSAT range by a factor of about 40
in X-ray ux and to substantially fainter optical magnitudes. While the bulk of the type-1
AGN population still follows the general correlation along a constant fX =f opt line, the type-2
AGNs cluster at higher X-ray-to-optical ux ratios. There is also a population of normal
galaxies emerging at low uxes (thus discovered in the Chandra and XMM era).
To be consistent with the already published deep ROSAT catalogs (Lehmann et al.
2001), we used a modied version of the X-ray to optical ux ratios:
log 10 (f x =f o )  log 10 (f 0:5 2keV =fR )  log 10 (f 0:5 2keV ) + 0:4R + 5:71; (1)
where the ux is measured in erg cm 2 s 1 units in the 0.5-2 keV band and R is in Vega
magnitudes. The slight change in the normalization (Maccacaro et al. 1988) is motivated
by the signicantly narrower X-ray energy band used (the original denition was based on
the Einstein medium sensitivity survey band, 0.3-3.5 keV), which introduces a factor of 1.77
decrease in the ux for objects with a spectral energy index of 1 (classical type-1 AGN)
and the use of the R-band instead of V (here we assumed a V R color of 0.22, typical value
for galaxies).
To use this new X-ray to optical ux ratio denition for source classication, we also had
to convert the canonical ranges (Stocke et al. 1991) to our new system. The new ranges

{ 6 {
for dierent classes of objects are shown in Table 2. To calculate the new ranges of the
X-ray to optical ux ratios, we assumed typical X-ray spectra for each class and calculated
the shift in the X-ray ux due to the narrower energy band: a power law with a photon
index of =1-2.7 for AGN, a power law with a photon index of =1-2 for BL Lac objects, a
Raymond-Smith model with kT =2-7 keV, abundances of 0.1-0.6 and redshifts of z =0-1. For
stars and supernova remnants we used Raymond-Smith models with energies of kT =0.5-2
keV, for X-ray binaries powerlaw models with photon index =1-2. For galaxies, we adopted
a somewhat ad hoc shift of 0.1-0.3 in the logarithm of the ux due to the dierent energy
bands. This choice was motivated by examining dierent models for galaxies (warm and
hot plasma mixture, powerlaw like emission from X-ray binaries, typical supernova remnant
spectra, etc.).
For the shift in the optical ux (using R-band instead of the canonical V-band) we
assumed typical values for each class.
The resulting ranges of the X-ray-to-optical ux ratios are shown in Table 2. As can
be seen from the table, the new X-ray-to-optical ux ratio is not signicantly dierent
from the canonical one. The typical ranges are a bit wider, but this just a consequence of
converting the ranges instead of directly determining it from large surveys. With our new
normalization, we can use the original ranges (Stocke et al. 1991) to make an educated
guess on the galactic/extragalactic nature of objects.
4. TARGET SELECTION
Target selection was primarily based on our deep VLT/FORS imaging data (Giacconi
et al. 2002), reaching a depth of R  26:5. In regions not covered by this VLT/FORS deep
imaging, we used somewhat shallower VLT/FORS imaging in the R-band obtained as part
of the survey.
Possible optical counterparts of X-ray sources were selected based on the estimated
astrometry error of the X-ray object (for a relatively bright point source at zero o-axis
angle the astrometry rms error is  0: 00 5). We used the automatically generated optical
catalog, however, every object was visually inspected for deblending problems and artefacts.
The surface density of our X-ray objects is very well suited to MOS spectroscopy with
FORS/VLT. We could ll a large part of the masks with program objects and it was quite rare
that we had to choose between multiple optical counterpart candidates within the geometrical
constraints of the instrument. As a consequence, our target selection is nearly unbiased.
The only selection eect that should be considered was related to objects with multiple

{ 7 {
counterpart candidates. In these cases we usually selected the object in the appropriate
magnitude range for the particular mask, but in general we tried to revisit these objects {
unless the rst one turned out to be clearly the counterpart.
We also took advantage of the extremely high accuracy of the robotic masks: in some
cases, we recongured some of the slits between read-outs, without changing the telescope
pointing to observe many (brighter) optical counterparts. This way, the integration time on
bright objects could be shortened and we could use the remaining time on a dierent object,
while maintaining longer integration times for the faint ones.
During our last two runs (in November and December 2001) we were also using the
prefabricated masks (MXU mode { only available for FORS2), as opposed to movable robotic
slitlets (MOS mode). For our survey, the only important dierence between the two modes
is more freedom in the placement of slits in MXU mode. This improved our observing
eôciency in the later phase of the survey, where we concentrated on fainter objects (with a
higher surface density).
4.1. The Reliability of the Target Selection
The reliability of X-ray follow-up surveys using optical (or near infrared) spectroscopy
hinges on matching the X-ray source to the right optical object. This is primarily done
through astrometry. Just how reliable are these identications? Using deep galaxy number
counts (Metcalfe et al. 2001), we expect roughly 0.02 galaxies in every square arcsec area
that are brighter than R  26. Considering our best 3 astrometry error (1: 00 5), we expect
 0:15 eld galaxies to fall within our error circle { even in the best, zero o axis angle
case. In other words we expect one false candidate for every seventh X-ray object at R
< 26. Considering the roughly 250 X-ray sources we observed, we expect that for at least
35 of them, there will be a completely unrelated faint galaxy, even in an error circle of 1: 00 5.
Fortunately, the X-ray counterpart candidates typically have much brighter magnitudes (see
Figure 2). At these brighter magnitudes the probability of eld galaxy contamination is
much lower, so we should only worry about contamination for very faint (R=25-27) objects.
As our astrometric accuracy heavily depends on the signal-to-noise ratio of the object
(i.e. objects with low photon counts are centered with lower accuracy) and the o-axis angle
of the object (there is a signicant degradation of the PSF of increasing o-axis angles), the
total area covered by the sum of the error circles is quite large, around 3900 arcsec 2 . In
Figure 2, we show the magnitude distribution of our selected primary optical counterparts
and the expected magnitude distribution of random eld galaxies over this area, based on

{ 8 {
galaxy number counts (Metcalfe et al. 2001; Jones et al. 1991). Contamination by random
eld galaxies becomes a serious problem beyond R  24 and they start to dominate beyond
R  26, the practical limit of our imaging survey.
Therefore, extra caution is required in making sure that the right optical object is
identied as the counterpart. This is not always trivial as the optical spectra do not always
show clear signatures of active nuclei (AGNs). In some cases we had to observe every object in
the error circle. Fortunately this turns out to be feasible. At R  24 and fainter, deblending
is not a serious challenge (using both automated and visual tests). At brighter magnitudes,
where deblending would be near impossible (e.g. detecting a R  25 X-ray object in the
halo of a R  19 galaxy), the probability of eld galaxy contamination is negligible. Stellar
contamination is negligible at our high galactic latitude.
It is also important to point out that these estimates of eld galaxy contamination are
for the probability of nding an unrelated object in our X-ray error circle. We can also ask
a technical question: what is the probability of nding a eld object on a slit? Taking a
20 00  2 00 area (the typical slit length in FORS-1 is around 20 00 ), we expect to nd a R < 23
galaxy in 5% of the slits and we expect statistically a eld galaxy with magnitude R < 25
in every second slit. This means that one has to be extremely careful in the data reduction
and do a very careful book keeping in the process.
5. OBSERVATIONS AND DATA REDUCTION
Data were obtained during 11 nights in 2000 and 2001. A summary of the observations
is presented in Table 4. All observations were using the `150I' grism (150I+17 in FORS-1
and 150I+27 in FORS-2). These grisms provide a pixel scale (dispersed) of 280  A/mm, or
roughly 5.5  A/pixel. The nominal resolution of the conguration is R = =
=230, which
corresponds to roughly 20  A at 5600  A. The pixel scale of these instruments is 0.2 00 /pixel, so
there is no signicant degradation of the resolution due to the nite slit width.
In the initial phase of our survey, we exclusively used low resolution multiobject spec-
troscopy with varying integration time. This strategy maximizes the number of observed
objects and provides a (nearly) full spectral coverage for every exposure. This is clearly
a trade o, as we then get a signicantly lower S/N spectrum for the individual objects,
compared to higher resolution long-slit spectroscopy based on photometric redshifts, but the
latter technique was deemed to be prohibitevely expensive in observing time in the initial
phase of our project.
As our goal was to observe as many objects as possible, we used non standard order

{ 9 {
separation lters (either no lter, or the GG-375 lter, which cuts out light bluer than
3750  A). It was thus possible to cover a very wide spectral range in a single exposure (in
the standard conguration the order separation lter that cuts the light blueward of 5900  A,
thus the whole spectral range can only be covered in two exposures).
5.1. Data Reduction
Data were reduced by our own semi-automatic pipeline built on top of IRAF. In general
we followed standard procedures, but had to deviate slightly in several cases to accomodate
particularities of the FORS instrument and do a very rigorous book-keeping. In the following
sections, we enumerate these changes.
5.2. Bias, Overscan and Trim Correction
The FORS CCD's have in principle 4 read-out modes: high and low gain and one and
four amplier modes. To avoid serious complications, we only used the high gain/one am-
plier read-out mode for our spectroscopic observations. This decision resulted in a slightly
larger overhead, but this was deemed negligible considering our long integration times, com-
pared to the challenges posed by reducing a 4 amplier read-out mode spectroscopic obser-
vations, where we would have to calibrate the gain of each amplier very accurately (so we
do not introduce artical features in the spectra).
A suôcient number of full frame bias exposures were taken during each run (typically
around 20 per run). These were individually overscan corrected and trimmed. The resulting
(bias) frames were averaged with suspect pixels (too high or too low values) ltered out to
generate the master bias frame. In each case we veried that the bias frame does not change
signicantly from night to night within a run.
A slight complication was posed by our spectrophotometric standard observations.
These frames were also using one amplier/high gain, but (to save some time) only 500
rows were read out (centered on the standard star). Since ESO does not provide an un-
der/overscan region for windowed frames, we took a suôcient number (typically 10) of bias
frames in this conguration. Naturally (lacking under/overscan region) these frames were
not overscan corrected, nor trimmed. Instead, they were averaged to create a master bias
frame, which did include the articially introduced bias level. We checked the individual
frames and conrmed that the variation of this artical bias level is negligible for these very
high S/N frames.

{ 10 {
After creating the full and windowed bias frames, all object and calibration ( at and
arc) frames were overscan corrected and trimmed (except the windowed frames) and zero
subtracted.
At this point we applied a shift in the dispersion direction, based on the slit position,
to bring (very crudely; within 10 pixels or 50  A) the observations on a similar wavelength
scale. We also inserted gaps in the spatial direction between the neighbouring slits to reduce
the risk of contamination between slits. These two steps are purely practical, but make
bookkeeping signicantly easier.
5.3. Flatelding
In this processing step, we had to tackle three main issues:
The rst one is an inherent complication in the FORS instruments. Due to the mechan-
ical construction of the robotic slit masks and the location of the at-eld lamps, at-eld
exposures show higher ux levels in a few rows at the upper or lower edge of the slit. To
correct for this eect, there are two sets of at-eld lamps in the instrument. We took a
suôcient number of at-eld exposures using both sets of lamps. We generated merged ats
independently for each lamp set and generated the nal at-eld frame by taking the smaller
pixel value in the two frames. As the re ections from the two lamp sets do not overlap, this
feature can be fully removed.
The second issue is a consequence of our unusual observing strategy. In some cases
(due to geometric constraints imposed by the robotic slit masks) we could not target very
faint objects with a particular slit, but we had several bright candidates available. In these
cases, to maximize eôciency, we recongured these slits between readouts so that all bright
candidates were observed, while faint objects targeted with other slits were observed with a
longer integration time. Due to the extremely high mechanical stability of the FORS instru-
ments, this strategy is very safe. As the sensitivity variation between pixels is potentially
color dependent, we decided to generate at-eld frames for each mask. This may not be the
optimal strategy since for the slits that are in the same position in two masks, we could use
more exposures, thus to create a more accurate at-eld. This alternative strategy would be
too complex and the resulting data quality improvement is very marginal, consequently we
decided against it.
The last major issue is due to the extremely wide spectral coverage used. As our in-
tention was to correct only for the pixel-to-pixel sensitivity variations, we had to generate a
normalization image (a combination of the at-eld lamp spectrum and the overall quantum

{ 11 {
eôciency of the system as a function of wavelength and spatial position). For high resolution
(and smaller wavelength coverage) observations, this is often achieved by collapsing in the
spatial direction and tting a function in the dispersion direction. Unfortunately, this tech-
nique proved to be impractical for us. The main problem was that we were unable to nd
an ansatz function that could reproduce the very sharp cutos at both ends (due to either
the order separation lter or the natural cut-o of the CCD detector) without introducing
artical structure on intermediate scale. An additional complication was that the internal
at-eld lamps did not illuminate the slits homogenously { there is a slight gradient in the
spatial direction. Therefore, after a slight smoothing of the at-eld exposures, we created
the normalization image by a linear or (for very long slits) a second order polynomial t in
the spatial direction. Each at-eld exposure was divided by this normalization frame, thus
creating a `true' at-eld frame, which only contains pixel-to-pixel sensitivity variations. In
regions, where the signal was too low, the at-eld was articially set to one (to avoid the
introduction of too high photon noise).
After these steps, the individual, normalized at-eld frames were merged, eliminating
the eect of light re ection on the slit edges. Both science and wavelength calibration frames
for a given mask were divided by the resulting master at-eld frame.
5.4. Sky Subtraction
The sky background was estimated in each column by a linear t (for longer slits) or
just calculating the average (shorter slits) in each column of each slit, rejecting too high
pixels (i.e. the targeted object) and subtracting the result. It is important to note that
we did not correct for the very slight curvature of the dispersed spectra on the CCD in this
step. With the FORS instruments, this strategy works quite well (as opposed to LRIS on the
Keck telescope). Signicant sky residuals are only present around the very bright, narrow
sky lines { where sky subtration is doomed anyway due to pixel saturation.
This procedure works only for our typical faint objects. Extremely bright objects can
illuminate the whole slit, thus making correct sky subtraction impossible. Fortunately, in
those (very few) cases identication was still possible due to the extremely high object signal.
5.5. Fringe Removal
In some cases (especially in MXU masks), we could take advantage of our dithering
strategy to reduce further the eect of fringing and the sky residuals. As neither the fringe

{ 12 {
pattern nor the sky residuals are signicantly aected by the small (spatial) osets of the
telescope, we could, in some cases (with suôcient number of exposures in a given mask)
exclude (most of) the object signal and create a fringe/sky residual template for each slit.
Subtracting this from the frames resulted in an improved signal-to-noise ratio for the object
spectra. Depending on the seeing conditions and the dithering osets used, not all object
signal was perfectly removed, thus the extracted spectra signicantly underestimated the
real spectra. As our primary goal was object identication, not spectrophotometry, this was
an acceptable trade-o.
5.6. Coadding the Frames
After sky subtraction, all the slits were visually inspected to verify that the object is
indeed in the 'good' region of the slit. This step was necessary since the applied small spatial
osets between the science exposures can result in objects falling too close to the slit edge
(MOS blade corners are round, thus the slit is not usable there) or falling completely outside
the slit.
After this visual screening, the spatial oset between dierent exposures of the same
object was caculated based on the world coordinate system (WCS) information stored in the
frame headers. The individual exposures were coadded (including the rejection of suspicious
pixels or cosmic ray hits) after applying these spatial shifts. We only shifted the frames in
the spatial direction and only by integer number of pixels. As the objects were suôciently
well sampled (the pixel scale was signicantly smaller than the seeing), this step resulted
in nearly negligible bluring of the spectra, while preserving the statistical properties of the
exposures.
5.7. Extraction
Even though for sky subtraction we could safely ignore the slight curvature of dispersed
spectra on the CCD, for the extraction of the object signal this is no longer possible. There-
fore, we estimated the object position on the detector by collapsing at least 30 columns
(more for really faint objects) in the dispersion direction and measuring the object center in
the resulting prole. The object position was tted typically with a second order polynomial
as a function of column (wavelength).
Then an aperture width was visually determined. Except in special cases (e.g. blended
objects), our aim was to include most of the object signal without adding too much sky (to

{ 13 {
maximize the signal-to-noise ratio). A one dimensional spectrum was obtained using the
`optimal extraction' method of IRAF. This procedure calculates a weighted average in each
column, based on both the estimated object prole and photon statistics.
5.8. Wavelength Calibration
Wavelength calibration was based on (daytime) arc calibration frames, using four arc
lamps (a He, a HgCd and two Ar lamps) which provide a suôcient number of lines over the
whole spectral range used (3889{9924  A).
The exact same aperture that was used for the science object was used for the arc
frames. The resulting lines were rst identied automatically. These identications were
then visually veried, and quite often signicantly improved. In most cases, around 20 lines
were located in the 3889{9924  A range, and tted by a forth order polinomial, with a typical
rms accuracy of 1  A or better. This accuracy is close to that expected from the nominal
resolution of the instrument in our conguration. The object spectra were then wavelength
calibrated and subsequently rebinned to obtain spectra with a linear wavelength scale.
We also examined the stability of the instrument by repeating the daytime calibrations
on dierent days. No noticeable change was detected. In addition, we veried the wavelength
calibration by checking the position of narrow skylines in science exposures { no discrepancy
was found within our error estimates.
The wavelength calibration may not be accurate in the range outside the two extreme
arc lines identied. As the FORS instruments use a grism, we had to resort to high order
polynomial ts, which become unreliable when extrapolating the wavelength solution. In
most cases, this is not an important issue, but there were a few unfortunate cases where
major object features fell into unreliable regions (typically if the spectra were cut short on
the blue side due to the position of the slit).
6. FLUX CALIBRATION
In this step, we nearly followed standard practices. The only signicant necessary change
arrised due to our choice of a non standard instrument conguration, namely not using the
right order separation lters. Consequently, we nearly doubled our eôciency (taking only
one exposure per object), but we then had to correct for second order diracted light.
It is important to point out that we have to correct for this eect both for the science

{ 14 {
and the spectrophotometric standard observations.
6.1. Second Order Diraction
The rst step was to determine the nature of the second order contamination. As
this contamination aects the red part of the spectrum, where there are typically many lines
present already from rst order diraction (in both arc and sky exposures), we used a special
set of calibration frames: a 1.3 arcsec wide long slit, the standard arc lamps (He, HgCd, Ar)
and a set of (dispersed) exposures through all available broad-band lters (U, B, V, R and I)
as well as without any lter. Using the exposure without lter, we established the rst order
wavelength solution of this conguration. We veried that the use of the Bessel lters does
not introduce any noticable shift in this solution. We were then able to identify the second
order lines in the exposures taken through the broad-band lters. These identications are
shown in Table 3.
The comparison between the apparent uxes in rst and second order diracted lines
indicates that second order diraction can be very strong, as much as 30% of the rst
order strength (especially in the blue part of the spectrum). This eect is made seriously
worse by the quantum eôciency of the CCD. The overall quantum eôciency of the system
peaks around 6000  A and declines relatively rapidly (see also Section 6.2). Because of this, a
relatively weak second order contamination may become the dominant signal beyond 9000  A
{ due to to the much higher sensitivity of the pixels to these photons. For blue objetcs
(for example spectral photometric standards), this problem is even worse: second order
contamination can already start at 7000  A(due to the high UV ux of the object) and can
contribute over 30% to the observed ux.
To correct for the second order diraction, we rst had to model it. Based on the
identied arc lines, we adopted a second order wavelength solution in a linear form:
 = 2:106 723  A; (2)
where  is the real wavelength of the feature and  is its apparent wavelength position
observed in second order.
It should be noted that, as opposed to grating spectrographs where the coeôcient is
practically two and the shift is very small, a few times 10  A (Gutierrez-Moreno et al. 1994),
FORS, which uses grisms, is signicantly dierent, which makes the detection of second
order diraction harder, unless one takes the appropriate calibration data sets.

{ 15 {
We assumed that the measured signal, d() is
d() = f()s() + c()f(); (3)
where s() is the overall quantum eôciency of the system,  is the real, physical wavelength
of features detected at  in second order, c() is the strength of the second order folded into
the sensitivity function at  and f() is the real spectrum of the object.
Since we can not derive two functions (s() and c()) from a single measurement, either
we determine the sensitivity, s(), independently (e.g. observing a standard star through
dierent order separation lters) or we use two independent measurements from observing
two dierent standard stars. As the rst option implies the introduction of an additional
optical element (the lter), which can aect the strength of the second order diracted signal
(in fact comparing the ux ratios of the 3650.1  A arc line in Table 3 is a strong indication for
this to be the case), we selected the latter aproach. We observed two standards with very
dierent spectral shapes, LTT-3218 (Hamuy et al. 1992, 1994, a relatively red DA6 white
dwarf) and HD49798 (Turnshek et al. 1990, a blue sdO6 subdwarf).
Given two dierent standards (f 1 () and f 2 ()), but identical instrument setups (c()
and s()), we can write
c() = d 1 () f 1 ()s()
f 1 () = d 2 () f 2 ()s()
f 2 () ; (4)
which we can solve for c():
c() = d 1 ()
f 1 ()

1 () ()
() ()

; (5)
where () = f 2 ()=f 1 () (known a'priori) and () = d 2 ()=d 1 () (known from observa-
tions).
The derived c() indicates that the contamination is completely negligible up to 6300  A.
Up to 7500  A it is somewhat stronger, but typically still negligible as this wavelength cor-
responds to up to 3800  A in rst order, where the CCD is very ineôcient. Between 7500
and 9000  A, the eect is strong (12% to 3% of the rst order instrumental ux shows up in
second order). Depending on the object type (whether it is a blue or red object) and the
wavelength of interest (as this result should be folded with the system quantum eôciency,
which is increasing with wavelength for second order diracted photons and decreasing for
rst order diracted photons in this range) this may or may not be a strong eect { this
decision should be made for each observing program. Beyond that this eect could not be
estimated as one of our standards is measured only to 8700  A. As in this range the CCD QE

{ 16 {
is dropping very sharply, while the rst order QE is very high, second order contamination
must become the dominant source of signal at some wavelength.
The eect of the second order diraction is demonstrated in Figure 3, using a blue
spectrophotometric standard star, Feige110 (Hamuy et al. 1992, 1994; Oke 1990).
6.2. Overall Quantum Eôciency of the System
The overall throughput of the system was determined using a set of spectro photometric
standard stars: LTT-377, LTT-3218, LTT-7379, LTT-7987, LTT-9239 (Hamuy et al. 1992,
1994), HD49798 (Turnshek et al. 1990) and Feige110 (Hamuy et al. 1992, 1994; Oke 1990).
These objects were observed repeatedly over a wide range of airmasses during each run,
using a simulated very wide ( 5 00 ) long slit, using the robotic mask facility of the FORS
instruments (combining 3 slits).
The observations were reduced nearly the same way as science observations. Second
order diraction was removed as outlined in Section 6.1. The measured spectra (in instru-
mental units) were compared to the published physical spectra { excluding regions with sharp
features in the objects and sharp telluric absorption features in the atmosphere. A smooth
sensitivity curve was tted to the data points. As we were using about the whole wavelength
range of the CCD, this t was done in four parts: 3000-4000  A (or 3500-4000  A if the OG375
order separation lter was used during the run), where the throughput raises very sharply
and only a 10% accuracy was achieved, between 4000-5000  A, where the throughput is still
rising fast (about 4% accuracy), between 5000-8000  A (2% accuracy) and nally between
8000-9500  A, where the accuracy drops again to around 10%. These four data sets were used
to construct the sensitivity curve for each observing run and each conguration.
As the Paranal Observatory does not have suôcient data collected to measure an ac-
curate spectroscopic extinction curve, we used the curve published by the Cerro Tololo
Inter-American Observatory (CTIO), after verifying, using our standard observations, that
the curve is very close to that estimated for Paranal.
This calibration was applied to all measured program spectra. We also corrected for
atmospheric extinction using the CTIO extinction curve. The accuracy of the resulting ux
calibrated (but not absolute calibrated { see below) spectra is mainly constrained by the
signal-to-noise ratio of the object signal in the 4000-8500  A range (the inaccuracy due to the
sensitivity function is negligible in this range). Outside this range the ux calibration can
introduce signicant structures as the throughput of the whole system drops very rapidly,
thus even very small inaccuracies in the wavelength calibration of the object spectra result

{ 17 {
in signicant over or underestimation of the physical spectra. It is also important to point
out that no attempt was made to correct for telluric absorption: For the vast majority of our
program objects, telluric absorption completely eliminates the signal (between 7600-7630  A,
7170-7350  A and 6868-6890  A), thus a correction is not practical. For the few brighter objects,
this correction would have been possible, but was deemed unnecessary for identication of
the sources.
6.3. Absolute Calibration { Estimating the Slitloss
The purpose of our observations was to identify as many X-ray sources as possible with
the telescope time available. Therefore, no eort was made to collect data necessary for
absolute calibration of the spectra measured. Even though we did not use an elaborate
program designed for spectrophotometry, we can still estimate the accuracy of our derived
uxes.
The most important eect to be considered is slit-loss. To maximize the S/N of the
data, we tried to match the slit width to the expected seeing of the observations. Therefore,
a signicant fraction of the light from the object was excluded, but this was more than
balanced by the large reduction in the sky background, and thus the increase in the S/N of
the source.
We can easily estimate the eect of slit-losses from the high accuracy broad-band pho-
tometry. Using the ux calibrated spectra, we can directly calculate the AB-magnitude of
the object in any lter:
mAB = 2:5 log
R
d(log )f  S 
R
d(log )S 
48:60; (6)
where f  is the energy ux per unit frequency, S  is the overall throughput of the system
(telescope and instrument) in arbitrary units.
The rst step is to select the lter curve to use, S  . In practice, no system can replicate
the canonical Cousins-Johnson lter curves exactly. Even a perfect lter response curve
would be distorted by the non atness of the CCD detector. In many cases a slight deviation
from this lter response curve is acceptable, assuming that the spectrum of the object is
smooth and the slope is not very dierent from the slope of Vega. Unfortunately, these
assumptions do not hold for most of our objects as a signicant fraction of the ux is in
very sharp features. Therefore, we have to use the eective lter curve of our system used
to derive the broad-band magnitudes. Fortunately, the Bessel lter set used by ESO is a
suôciently good approximation of the Cousins-Johnson lters and the quantum eôciency

{ 18 {
curve of the FORS detectors being relatively at, this correction would only amount to a
fraction of a percent and can be safely ignored. Therefore, we used the published ESO lter
response curves folded over the quantum eôciency of the detectors as system throughput, S  .
To convert to Vega magnitudes, we calculated the AB magnitude of Vega from its spectra
(Fukugita et al. 1996). The resulting slitlosses are presented in Table 4 for point sources for
each mask. We also checked if the slitloss depends on wavelength (by comparing dierent
broad-band magnitudes) but found no signicant eect.
6.4. Reddening Correction
To calculate the eect of reddening due to our Galaxy on the spectra, we used the
100m maps (Schlegel et al. 1998). In the direction of the CDFS, l = 223:5 ô , b = 54:4 ô ,
the color excess is E(B V) 0:008. Assuming the canonical value, RV = 3:1 for the ratio
of extinction in the V-band to the color excess (Cardelli et al. 1989), the extintion is
A(U) 0:04 and A(I) 0:01. As this extinction is heavily dependent on the choice of RV ,
this correction was not applied to the data, introducing an articial tilt in all spectra on the
order of a few percent.
The AGN line strengths were not corrected for absorption lines from the host galaxy
(Ho et al. 1993) as the S/N of our faint spectroscopic sample is too low. Consequently, the
very few optical identications based on line ratios are possibly aected by this eect.
Correcting for reddening by the AGN host galaxy would require to estimate the ex-
tinction using the X-ray spectral information. This correction is deferred to a later paper
concentrating on X-ray spectral analysis of the CDFS sources based on the Chandra and
XMM-Newton data.
7. REDSHIFT DETERMINATION AND THE SPECTROSCOPIC SAMPLE
7.1. Redshift and Luminosity Determination
The rst step toward the classication of the spectroscopically observed sources was
their redshift determination. In the vast majority of the cases this was done through the
identication of prominent features, typically the 4000  A break and the Ca ii H and K ab-
sorption, Balmer lines or emission lines (e.g. Ly-, C iv, C iii], Mg ii, [O ii], etc.). In case
of prominent emission lines, the wavelength ratio of the line centers was used to identify
these features. In cases of single emission line objects with no additional feature, this line

{ 19 {
was usually identied as either [O ii] or Ly-, depending on the continuum spectral shape.
Naturally, these are not secure classications, the quoted redshifts should only be used as
an educated guess to optimize follow-up observations.
The redshift identications are summarized in Table 5. The `No' column refers to our
internal id of the X-ray source { this is the unique detection ID (XID) in the published
catalog (Giacconi et al. 2002). In cases of multiple counterparts, a letter is appended
to this number to distinguish between the optical candidates. Extended X-ray objects are
marked with a star. When an object was observed repeatedly, multiple entries are given in
the table. Altogether 249 X-ray sources were observed, of which one point source belongs
to the small additional sample given in Table 1, and 15 are extended X-ray sources. In 17
cases, the slit was centered on the X-ray position for the search of strong, narrow emission
lines although no counterpart was detected in the R-band.
The mask column is our internal name used to identify the set of observations used for
individual objects. Multiple mask names indicate that during the observations some slits
were recongured, but the slit used for the object was identical during the set of observations.
The relevant observing conditions and conguration can be found in Table 4 (exposure time,
slit width, seeing, etc.).
The two position columns (right ascension and declination) give the coordinates of the
optical object, not those of the X-ray source. Astrometry is based on the USNO (Monet et
al. 1998) reference frame, just like the X-ray positions in Giacconi et al. (2002) and the
astrometric accuracy is better than 0.2 00 .
Whenever available, we also provide broadband optical information, an R-band magni-
tude and R K color (both in Vega magnitudes). If no R-band magnitude is given, it implies
that our FORS imaging data is not deep enough to measure the magnitude of the object (all
program objects are covered by the FORS R-band survey). The lack of R K color can be
due to our limited near-infrared coverage (NA entries).
Assuming (throughout this paper)
an
m =
0:3,
 = 0:7 universe and H 0 = 70 km s 1
Mpc 1 (Spergel et al. 2003) the total X-ray intrinsic luminosity of the object, LX , in erg
s 1 , is (Carroll et al. 1992)
LX (f X ; z) = 4fX
0
@ c(1 + z)
H 0
p
j
k j
sinn
0
@ p
j
k j
z
Z
0
(1 + ) 2 (1
+
m ) (2 +
)


1=2 d
1
A
1
A
2
(7)
where fX;tot is the observed X-ray ux in the 0.5-10 keV band. The sinn(x) function is sin(x)
for
k < 0, sinh(x)
for
k < 0 and simply x
for
k = 0,
where
k 
1
m
 . In case of

{ 20 {

k = 0, the two
p
j
k j terms disappear. This ux being the observed X-ray ux, it should
be interpreted as a lower limit for the intrinsic X-ray ux of the object due to potentially
strong obscuration of the source.
If we assume
that
k = 0
(i.e.
m
+
  1), we can rewrite this equation as
LX (f X ; z) = 4fX
0
@ c(1 + z)
H 0
0
@
z
Z
0
(1 + )
3
m
+


1=2
d
1
A
1
A
2
(8)
Introducing x = (1 +
)(
m
=
 ) 1=3 , this simplies to
LX (f X ; z) = 4fX c 2 (1 + z) 2
H 2
0

2=3
m

1=3

0
B @
(1+z)(
m=
 ) 1=3
Z(
m=
 ) 1=3
dx
p
x 3 + 1
1
C A
2
(9)
The above integral can be evaluated in terms of incomplete elliptical integrals of the rst
kind. We also give below an analytical t for at cosmologies (Pen 1999)
with
m = 0:3:
dL = c(1 + z)
H 0

3:308 3:651 0:207 + 0:446(1 + z) + 0:757(1 + z) 2 0:204(1 + z) 3 + (1 + z) 4
1=8

(10)
In Figure 4 we show the correction to the calculated X-ray luminosity for slightly dier-
ent cosmologies. We also show the dierence between luminosities calculated using current
cosmological parameters and the (now
obsolete)
m =
1,
 = 0, H 0 = 50 km s 1 Mpc 1
cosmology,
LX = 4fX;tot

2c
H 0

1 + z
p
1 + z
  2
 1:72  10 58 cm 2 fX;tot

1 + z
p
1 + z
 2
; (11)
The HR column contains the already published (Giacconi et al. 2002) hardness ratios
for each object, HR = (H S)=(H + S), where H and S are the net count rates in the
hard (2-10 keV) and soft (0.5-2 keV) band, respectively. It is important to point out that
the hardness ratio is dened in instrument counts (for Chandra ACIS-I), thus for dierent
X-ray telescopes or instruments, it should be converted using their specic energy conversion
factors.
The z column gives our best redshift estimate. The selected low spectral resolution leads
to an uncertainty in the redshift determination of 0:005. For broad emission line objects the
uncertainty is signicantly higher. The quoted redshift value always refers to the particular
observation of the object, thus, there can be slight discrepancies between observations of the
same object or missing redshift values for some masks.

{ 21 {
7.2. The Optical and X-ray Classication
The classical/optical and X-ray classications of the objects are discussed in details in
Section 10 and given in Table 5.
Based on purely the optical spectra, we dene the following optical object classes:
 BLAGN: Objects with emission lines broader than 2000 km s 1 . This classication
implies an optical type-1 AGN or QSO, as discussed in Section 10.
 HEX: Object with unresolved emission lines and exhibiting high ionization lines or
emission line ratios indicating AGN activity. These objects are dominanly optical type-
2 AGNs or QSOs, but in a few cases the optical type-1/2 distinction is not possible
based on the data.
 LEX: Objects with unresolved emission lines consistent with an H ii region-type spec-
tra. These objects would be classied as normal galaxies based on the optical data
alone as the presence of the AGN can not be established.
 ABS: a typical galaxy spectrum showing only absorption lines.
 star: a stellar spectrum.
Our main classication is solely based on the observed X-ray properties (LX and HR)
of the sources and is summarized below. The type-1 AGN/QSO are soft X-ray sources,
while the type-2 AGN/QSO are hard, absorbed X-ray sources (for the relationship between
hardness ratio and absorption see e.g. Mainieri et al. 2002). The AGN and QSO classes
cover dierent ranges of X-ray luminosities.
 QSO-1: LX (0.5-10 keV) 10 44 erg s 1 and HR  0:2.
 AGN-1: 10 42  LX (0.5-10 keV)< 10 44 erg s 1 and HR  0:2.
 QSO-2: LX (0.5-10 keV) 10 44 erg s 1 and HR > 0:2.
 AGN-2: 10 41  LX (0.5-10 keV)< 10 44 erg s 1 (lower limit smaller than for the AGN-1
population to account for substantial absorption) and HR > 0:2.
 gal: LX (0.5-10 keV)< 10 42 erg s 1 and HR < 0:2.
 star: this class is dened from the optical spectra and/or proper motions.
Throughout the paper we call X-ray type-1/2 AGNs and QSOs together X-ray type-1/2
objects.

{ 22 {
7.3. The Spectroscopic Sample
The quality ag, Q, indicates the reliablity of the redshift determination. Q = 2:0
indicates a reliable redshift determination, a value of 0.0 indicates no success. Q = 1:0
indicates that we clearly detect some feature (typically a single narrow emission line) in
the spectrum that cannot be identied securely. In a few cases, Q = 0:5 is used when
there is a hint of some spectral feature. This quality ag only refers to the reliability of the
spectroscopic classication. The identication of the X-ray sources is unambiguous for single
counterparts in the X-ray error circles, and for cases with reliable redshift identication we
then use a Q = 2:0+ quality ag. X-ray sources with multiple counterparts are discussed
below. The Q = 2:0+ objects dene our spectroscopically identied X-ray sample.
Finally, the comments column contains additional information relevant to the particular
observation. The most common ones are a limited wavelength coverage (the full wavelength
range is not available due to the positioning of the slit) and the detection of high ion-
ization lines. We also include information necessary to apply the stricy Seyfert denition
(Khachikian & Weedman 1974) to optically classify our objects.
Among the X-ray sources with multiple optical counterparts, the identication is con-
sidered as highly reliable in the following 13 cases: X-ray type-1 QSO/AGN (XID 30, 101),
X-ray type-2 QSO/AGN (XID 56, 201, 263), and interacting galaxy pairs (XID 98, 138,
580). Four of the remaining X-ray sources (XID 553, 567, 582, 620) are the brightest objects
in the X-ray error circles, only detected in the soft band and at moderate redshift with H ii
region-type spectra, thus most likely the X-ray counterparts. The last source (XID 189) is
detected in the hard band only, has R K > 5 and is the brigthest, best centered counter-
part (the additional counterparts are very faint, R > 25). These objects are included in the
spectroscopically identied X-ray sample.
As the CDFS has been observed by various teams and covered by wide surveys (2dF
and Tycho), we could include in our sample additional spectroscopic redshifts. Four sources
(XID 39, 95, 103, 116) were in fact already published in the CDFS 130 ksec paper (Giacconi
et al. 2001). Eight objects (XID 33, 38, 149, 171, 204, 526, 563, 600) are covered by the
K20 survey (Daddi et al. 2003, Cimatti, private communications) and three (XID 90, 92
and 647) by the COMBO-17 survey (Wolf, private communication). Three sources have
optically bright, low z counterparts in the 2dFGRS (Colless et al. 2001). One ot them, XID
84 (TGS243Z005), has a soft X-ray spectrum and appears to be a normal X-ray galaxy. The
other two sources, XID 247 (TGS243Z011) and XID 514 (TGS243Z010), have hard spectra,
luminosities LX (0.5-10 keV)  10 40 erg s 1 and are o-centred within the parent galaxy:
these properties are similar to those of the brigther, ultraluminous compact X-ray sources
(ULXs) detected in nearby spiral galaxies (Makishima et al. 2000). Finally, one source

{ 23 {
(XID 549), optically very bright, is identied with an object (TYC 6453-888-1) from the
Tycho Reference Catalog (Hog et al. 1998), that has a clear proper motion (7.62.1 and
15.71.7 mas/yr in right ascension and declination, respectively) and is thus a star in the
Milkyway.
The spectroscopically identied X-ray sample comprises 137 sources of which 15 are
fainter than R = 24.0. Among the brighter objects, there are seven extended X-ray sources
at 0:6 < z < 1 (XID 132, 138, 249, 560, 566, 594, 645: Giacconi et al. 2002). In addition,
there are 24 X-ray sources with secure identications but only tentative redshifts (Q = 0:5
and 1.0 cases).
8. FINDING CHARTS AND SPECTRA
Figure 5 gives the nding charts and all the spectra obtained for each of our program
objects.
Finding charts are 20 00  20 00 in size, centered on the X-ray position with its 2 position
error circle. Individual contrast levels are chosen in each case to give as much information
as possible. If multiple optical counterparts are present in (or around) the error circle, they
are marked and labeled. The underlying optical images are our R-band FORS images.
Next to the nding charts, we show the associated spectra. For cases of repeated
observations, all the data are shown. In the plots, we mark the features used for the redshift
determination.
In cases of marginal line detections, we also examined the sky-subtracted coadded two-
dimensional frames to conrm/inrm the presence of the feature. These images are not in-
cluded in this paper, but are available through our web-site, http://www.mpe.mpg.de/CDFS.
9. FIELD SAMPLE
During our survey, we also collected a large number of eld object spectra. These were
objects either accidentally covered by some of our slits, or observed in slits that could not be
placed on X-ray counterpart candidates due to geometrical constraints, or stars used to align
the MXU masks. Consequently, this sample is not representative of the eld population.
The results of these observations are summarized in Table 7. We give the object position,
mask name, R-band magnitude (when available), redshift, redshift quality ag, very crude
classication and optional comments relevant to the observation. The full dataset (spectra

{ 24 {
and nding charts) is available on our web site (http://www.mpe.mpg.de/CDFS).
10. X-RAY VERSUS OPTICAL CLASSIFICATION
Seyfert galaxies (Seyfert 1943) were originally dened (Khachikian & Weedman 1974)
as a recognizable galaxy (on Sky Survey prints) that have broad (> 500 km s 1 ) emission
lines arising in a bright, semi-stellar nucleus. Seyfert galaxies were subdivided into class
1 and class 2, depending on the width of the Balmer lines, compared to that of forbidden
lines. For line widths 200 < FWHM < 500 km s 1 , additional criteria were applied, based
on emission line ratios (e.g. Osterbrock 1989) to establish the Seyfert nature of a galaxy.
With the emergence of the unied AGN model (Antonucci & Miller 1985), it is now widely
accepted that these two Seyfert classes are not distinct, but form a continuous distribution
between the two extremes and a large number of intermediate classes were introduced since
the original denition. Applying these classical denitions poses very serious problems for
the study of faint X-ray sources.
At high redshifts, the Balmer lines are no longer in the optical range: the two strongest
Balmer lines, H and H, are redwards of 8500  A for z > 0:3 and 0.75, respectively. This
problem was overcome by extending the original denition to permitted lines in the UV
range from Mg ii2796,2803 to Ly (see e.g. Schmidt et al. 1998), thus allowing an optical
classication of objects up to z  6:5. Another diôculty stems from the fact that most
of the objects associated with faint X-ray sources are at intermediate redshifts and, thus,
are comparable in size to the seeing achievable with ground-based optical telescopes. As
a consequence, we can only study the integrated emission from these objects, as opposed
to nuclear emission from local Seyfert galaxies. Consequently, the nuclear emission can
be `hidden' in the stellar light coming from the host galaxy. The study of local Seyfert
galaxies conrms that about 60% of the local Seyfert type-2 galaxies would not be classied
as Seyfert-2, if only the total emission were available (Moran, Filippenko & Chornock 2002).
Moreover, an obvious challenge in applying the classical Seyfert denition for faint
objects is merely to recognize that they are AGNs. The main optical classes introduced in
this paper for extragalactic sources are: 1) BLAGN { FWHM(permitted lines)> 2000 km
s 1 , 2) HEX { unresolved emission features but presence of high excitation lines not found
in H ii regions (e.g. [Ne v]3425, He ii1640), suggesting AGNs of the optical type-2 class,
3) LEX { H ii region-type spectrum, 4) ABS { typical galaxy absorption line spectrum. For
the 130 extragalactic X-ray sources with secure redshift identication, there are 32 BLAGN,
24 HEX, 54 LEX and 21 ABS sources, thus 57% LEX+ABS objects. But among the latter
(optically dull), it should be noted that there is a large number of luminous X-ray sources.

{ 25 {
To overcome the limitations of the classical/optical denition of AGN, we follow the
unied AGN model introduced by Antonucci & Miller (1985) and classify an object as an
AGN if it has (nuclear) emission stronger than expected from stellar processes in normal
galaxies. This emission is likely to be produced by strong accretion onto supermassive
objects, most probably black holes. A clear signature of the presence of this accretion is a
high X-ray luminosity.
An X-ray classication requires rst to introduce a conservative lower limit on the
(unabsorbed) absolute X-ray luminosity of AGNs. Local, well studied starburst galaxies
have X-ray luminosities in the 0.5-10 keV band typically below 10 42 erg s 1 (Rosati et al.
2002; Alexander et al. 2002). Thermal haloes of galaxies and intragroup/cluster gas can
have higher X-ray luminosities but, in Chandra data, they are spatially resolved and detected
only in the soft band thus, at intermediate redshifts, they become fainter than 10 42 erg s 1
in the 0.5-10 keV band. Accordingly, objects with LX (0.5-10 keV)  10 42 erg s 1 , should
be classied AGNs. There are 20[20] HEX, 31[53] LEX and 9[12] ABS (excluding XID 645
which only shows extended X-ray emission) high LX sources with secure[secure+tentative]
redshift identication respectively. Thus the optical classication completely fails to identify
as AGN 42% (LEX+ABS fraction) of the luminous X-ray sources (96), or altogether 54% if
we include the tentative redshift identications (120). In these objects, optical extinction of
the nuclear component by dust can be very high, and/or the host galaxy can outshine the
central AGN (Lehmann et al. 2000, 2001).
The X-ray luminosity is also used to separate the sources of the AGN class, 10 42 
LX (0.5-10 keV) < 10 44 erg s 1 , from those of the QSO class, LX (0.5-10 keV)  10 44 erg s 1 .
Secondly, following the unied AGN model, we can also dene two AGN classes by using
the hardness ratio, a parameter sensitive to X-ray absorption which can be measured even
for faint objects. In Figure 12, we give the expected hardness ratios for AGNs with power
law X-ray spectra, selecting a photon index =2 and dierent absorption levels. Unabsorbed
sources have HR  0:5, independent of z. This is indeed the case for all the BLAGNs;
their hardness ratios are in the range 1:0  HR  0:2, except for one BAL QSO. The
scatter is easily explained by introducing dierent slopes for the X-ray spectra, together with
statistical errors associated with low number counts in the X-ray bands. The harder spectra
(HR > 0:2) are fully consistent with absorbed power law spectra. Signicant intrinsic
absorption, 10 21:5 < NH . 10 23:5 cm 2 , has indeed already been found for the type-2 AGN
population (Mainieri et al. 2002; Barger et al. 2002). Figure 12 shows that, assuming
= 2, intrinsic absorption (HR > 0:2) can be detected up to z = 0.25, 2.1 and 3.9 for
NH = 10 22 ; 10 23 and 3  10 23 cm 2 , respectively. Thus the hardness ratio can be used to
separate the unabsorbed sources, X-ray type-1: HR  0:2, from the absorbed ones, X-ray

{ 26 {
type-2: HR > 0:2. Indeed, in the Chandra and XMM-Newton deep surveys, most of the
harder X-ray sources are optical type-2 AGN with an increasing fraction of absorption at
decreasing X-ray ux (Barger et al. 2001a,b; Hasinger et al. 2001; Rosati et al. 2002;
Mainieri et al. 2002). Among this class of objects, there are a few bright type-2 QSOs but
the majority of the sources are type-2 AGNs at z . 1 (see e.g. Hasinger 2002). It should be
noted that an X-ray classication based on the hardness ratio might be misleading for some
high-redshift objects: an increasing absorption makes the sources harder, while a higher
redshift makes them softer. Consequently, some high-redshift absorbed/type-2 sources may
be mistakenly identied as type-1, but not the other way around.
A consistent X-ray classication should use the intrinsic luminosity. As mentioned
above, hard sources (HR > 0:2) at z  0:25 have absorbing column densities NH  10 22
cm 2 and thus their de-absorbed ux in the observed 0.5-10 keV band is at least 5 times larger
than the observed ux. Consequently, hard objects (HR > 0:2) with lower luminosities
((10 41 < LX (0.5-10 keV) < 10 42 erg s 1 ) can be classied as X-ray type-2 AGN. Four
additional objects (XID 55, 525, 538, 598) are thus classied as low LX X-ray type-2 AGNs.
In Figure 13, we show the hardness ratio versus the observed X-ray luminosity for all
the sources with secure redshift, for both the optical classication (left panel) and the X-ray
one (right panel). No source with a very high X-ray luminosity is present in this diagram:
this is, at least in part, a selection eect of pencil beam surveys. We now compare the optical
and the X-ray classications.
 Of the 32 BLAGNs in our sample, all are X-ray type-1 objects, except the BAL QSO
(XID 62, HR = 0:07) which is an X-ray type-2 QSO.
 Among the HEX population (24 objects), there are 16 X-ray type-2 AGNs/QSOs
(including one low LX source: XID 55) for which X-ray absorption is indeed associated
with optical obscuration. There are eight X-ray type-1 AGNs/QSOs or galaxies, of
which four at z  1:6 (XID 31, 117, 563, 901) with permitted emission lines no broader
than  1500 km s 1 . These four sources may be partly absorbed (NH = 10 22 -10 23
cm 2 ), thus misclassied as X-ray type-1: the presence of probable X-ray absorption
should be conrmed by X-ray spectral analysis, whenever possible. In the spectrum
of XID 34a, we do not detect permitted lines. The remaining three HEX objects are
X-ray galaxies (XID 98a, 175b, 580a), two being members of interacting pairs, and all
have HR = 1:0. They could be either low LX type-1 AGN or, in the case of the
interacting pairs, shocks might be at the origin of the [Ne v] emission.
There is a high fraction, 42%, of z > 2 sources among the HEX class as compared to
25% in the BLAGN class.

{ 27 {
 The LEX population comprises 54 sources with secure redhift identication, of which
9 and 24 X-ray type-1 and type-2 (including two low LX sources: XID 525, 538)
AGNs/QSOs, respectively. The optical classication thus fails to identify as AGN 61%
of this population. Among the remaining sources, there are 21 X-ray galaxies including
one ULX (XID 247) at z = 0:038 with a hard spectrum, HR = 0:31 (see Section 7). In
the LEX class, there are only two high luminosity sources of the X-ray QSO class and
no objects at high redshift (z > 1:5). A few X-ray type-2 AGNs might be of the HEX
class but, due to the low S/N (< 5 per resolution element) of their optical spectra,
high excitation lines could be below the detection threshold.
For most X-ray type-2 AGNs, both the broad (BLR) and narrow (NLR) emission
line regions could be obscured by dust absorption. Alternatively, the obscuring region
may fully cover the central UV source and the BLR, preventing photo-ionization of
external regions thus the existence of a NLR. The AGN nature of all the X-ray type-1
sources (0:53  z  1:03) is diôcult to ascertain from the optical data alone as the
H line is outside the observing range for redshift higher than 0.4. For six of them,
the expected Mg ii emission line is within the observed range (i.e. 0:4 < z < 2:2) and
away from strong sky lines, but the S/N is not high enough to detect a weak broad
line; in one source (XID 138), a broad Mg ii emission line may be present, although at
a low signicance level. For comparison, Mg ii is often seen in absorption or with a P
Cygni prole in star-forming galaxies (Kinney et al. 1993).
 There are 21 sources in the ABS class of which one and 9 X-ray type-1 and type-2
(including one low LX source: XID 598) AGNs. Thus 48% of the AGN population in
the ABS class is missed by the optical classication. All the sources of the X-ray AGN
class are at z < 1:2. The 11 X-ray galaxies are all at z < 0:8 and have soft spectra
(HR < 0:7) except one object (XID 514), a ULX at z = 0:103 with HR = 0:14
(see Section 7).
The comparision of the two classication schemes are summarised in Table 8.
The proposed X-ray classication is more successful than the classical/optical one in
revealing the presence of black hole activity, whatever the amount of dust obscuration from
the central and/or external parts of the nuclear region. Thus, we use this classication
throughout the paper unless otherwise stated. For comparison, we also give the optical clas-
sication in Table 5. The latter may be more appropriate in studies that aim to extrapolate
the classical Seyfert denition to faint AGNs.
It should be noted that using the X-ray classication is mandatory to properly identify
the X-ray normal galaxies among the LEX+ABS optical class. This population provides

{ 28 {
another means to derive the star formation history of the universe, in addition to the methods
using radio or optical data.
11. CLUSTERS AND EXTENDED SOURCES
Of the 19 extended sources detected in the CDFS (Giacconi et al. 2002), 15 were
observed in our survey. In 5 cases (XID 37, 147, 522, 527 and 581) no spectroscopic identi-
cation was possible and in one case (XID 132) only a low quality identication was obtained.
In two cases (XID 116 and 514) the diuse X-ray emission could be ascribed to thermal halos
of nearby galaxies. In general, most of the remaining extended sources span the regime of
galaxy groups (with luminosities of a few10 42 erg s 1 ) down to X-ray luminosities typical of
thermal halos around single early-type galaxies. In some cases, either the hardness ratio or
the optical identication suggest the coexistence of a thermal halo with an AGN component
(e.g. XID 138). In Figures 6-11 we show K-band images of the identield clusters/groups
with overlaid Chandra contours (2.5,3,4,5,7,10  above the local background) in the [0.5-2]
keV band. We also mark objects with concordant redshifts (as listed in Table 5).
Specically, XID 566,594,645 are ordinary groups showing however a range of surface
brightness proles (see Figs. 9,10,11). XID 566 and 594 belong to the large scale structure
at z ' 0:73 (see below). XID 249, for which we have two concordant redshifts with < z >=
0:964, is clearly extended with a harder component (Fig. 7). XID 138 was identied as a
close pair of AGN at z = 0:97, surrounded by a soft halo. In two cases, XID 511 and 560,
we identied only one galaxy per source, making it diôcult to ascertain the existence of a
group.
12. REDSHIFT DISTRIBUTION
The spectroscopically identied CDFS sample comprises 135 X-ray sources, including
ve stars. Reliable redshifts can be obtained typically for objects with R < 25:5, however,
some incompleteness already sets in around R  23. For the R<24 sample (199 objects), 120
(including ve stars) of the 159 observed X-ray sources have been spectroscopically identied,
thus a success rate of 75% and a completenes of 60%. The sources with inconclusive redshift
identication cover a wide range of hardness ratios. In Figure 14, we show the spatial
distribution of the sources with spectroscopic observations as well as those not observed.
The latter lie predominantly in some of the outermost parts of the CDFS.
The histogram of the redshift distribution of the X-ray sources is shown in Figure 15.

{ 29 {
A preliminary version of this diagram was given by Hasinger (2002). There is an excess
of objects in two redshift bins, revealing large-scale structures of X-ray sources(Gilli et al.
2003), similar to that found in the CDFN (Barger et al. 2002). These redshift spikes are
populated by X-ray type-1 and type-2 AGNs as well as a few X-ray galaxies. There are 18
X-ray sources within 2000 km s 1 of z = 0:674, of which one (XID 201b) is fainter than
R of 24; these objects are distributed loosely across a large fraction of the eld and should
thus trace a sheet-like structure. The spike centered on z = 0:734 is narrower and includes
16 X-ray sources within 1000 km s 1 of the mean redshift, all brighter than R of 24. In
both structures, about 70% of the sources are X-ray type-2 AGNs (+ X-ray galaxies). The
brightest X-ray cluster (XID 594) belongs to the z = 0:73 spike. A few eld galaxies, possibly
associated with this X-ray cluster and other extended X-ray sources (of which XID 645 at
z = 0:679), are given at the end of Table 5. The z = 0:67 and 0.73 structures are also traced
by galaxies from the ESO K20 survey which covers 1/10 of the Chandra eld (Cimatti et
al. 2002a,b): they are populated by 24 and 47 galaxies respectively (Gilli et al. 2003).
The K20 structure at z = 0:73 is dominated by a standard cluster with a central cD galaxy
(identied with the extended X-ray source XID 566), whereas the K20 galaxies at z = 0:67
are uniformaly distributed across the eld. There is also evidence of higher redshift, narrow
spikes in the distribution of the X-ray sources at z = 1:04, 1.62 and 2.57; that at z = 1:04 is
also present in the K20 sample (Gilli et al. 2003).
At z > 2, there are similar numbers of X-ray type-1 (5) and type-2 (7) QSOs. The
relative paucity of high z X-ray type-2 AGN (1/6) could arise from an observational bias as
type-2 sources are optically fainter than the type-1 population. At z < 1, the higher number
of X-ray type-2 over type-1 sources is mainly due to the large concentration of X-ray type-2
sources within the z = 0:67 and 0.73 structures.
The redshift distribution of the bright sample with 60% redshift identication com-
pleteness can be compared to those predicted by models. The X-ray background population
synthesis models (Gilli et al. 2001), based on the AGN/QSO X-ray luminosity function
and its evolution, predict a maximum in the AGN/QSO redshift distribution at z  1:5.
Contrary to these expectations, accretion onto black holes is still very important at z < 1:
indeed 88 (68%) of the 130 CDFS extragalactic X-ray sources are at z < 1 and the redshift
distribution peaks around z  0:7, even if the normal starforming galaxies are removed
from the sample. Similar results were found for the CDFN (Barger et al. 2002). This
clearly demonstrates that the population synthesis models will have to be modied to in-
corporate dierent luminosity functions and evolutionary scenarios for intermediate-redshift,
lower-luminosity AGNs.
Moreover, the CDFS redshift distribution does not conrm the prediction by Haiman

{ 30 {
& Loeb (1999), that a large number (100) of QSOs at redshifts larger than 5 should be
expected in any ultra deep Chandra survey. The highest redshift in the CDFS thus far is
3.70, while there are two conrmed and one uncertain high redshift sources in the CDFN at
z = 4:14; 5:19 and z = 4:42, respectively (Barger et al. 2002, 2003a; Brandt et al. 2001b),
as well as one QSO at z = 4:45 in the Lockman Hole (Schneider et al. 1998). As our target
selection is based primarily on our R-band imaging, we are suering from a bias against z>5
objects (the Ly  emission is redshifted out of the FORS R-band at z5). Therefore, we
may have a few QSOs at redshifts larger than 5 in the sample, but we can be certain that
the number of these is on the order of a few. Most of the X-ray survey area is covered by
near-infrared, where objects well beyond redshift of 15 are detectable. Among the objects
covered in the near-IR, we only nd 10 that are detected only in the near-IR. Furthermore,
4 of these were still observed spectroscopically, where we can detect Ly  emission up to a
redshift of 6.5. So in the unlikely case that all these objects and ve additional objects not
detected in optical imaging and without near-IR coverage are all very high redshift QSOs,
we are still an order of magnitude below the predicted number of such objects. This suggests
a turn-o of the X-ray selected QSO space density beyond z  4 (Hasinger 2002; Barger et
al. 2003a).
13. OPTICAL AND X-RAY DIAGNOSTICS
13.1. X-ray and Optical Fluxes
The soft and hard X-ray uxes versus redshift diagrams are shown in Figure 16. The
X-ray type-1 and type-2 populations have similar hard X-ray uxes, whereas these two
populations cover dierent ranges of soft X-ray uxes, as can also be seen in Figure 1.
However, the brighter, rarer objects, fX (0.5-2 keV) and fX (2-10 keV) larger than (1 and
5)10 14 erg cm 2 s 1 respectively, are dominated by optically broad-emission line QSOs
(at z < 2) as already demonstrated by larger samples of luminous X-ray sources detected by
ROSAT, Chandra and XMM-Newton (Lehmann et al. 2001; Barger et al. 2002; Mainieri
et al. 2002).
The observed R and K magnitudes of the extragalactic sources versus redshift are shown
in Figures 17 and 18 respectively. At z & 2, there are seven X-ray type-2 QSOs (XID 27,
54, 57, 62, 112, 202, 263) plus one lower X-ray luminosity type-2 AGN (XID 642); except
the BAL QSO, all have narrow Ly and C iv emission, HR > 0:2, and faint optical
magnitudes R & 24:0. There are also six X-ray type-1 QSOs at z & 2 (XID 11, 15, 21, 24,
68, 117), all but one being otically bright (R < 24) BLAGN, and ve fainter, lower X-ray
luminosity type-1 AGN (XID 87, 89, 230, 563, 901). The fraction of high-redshift, X-ray

{ 31 {
type-2 QSO+AGN sources is thus 42%. Moreover, two of the X-ray type-1 QSO/AGN (XID
117, 901), with narrow Ly and C iv emission but HR < 0:2, could be absorbed X-ray
sources since the hardness ratio is not a good tracer of intrinsic absorption for high redshift
sources. These results dier from those obtained for the CDFN 2 Msec sample (Barger et al.
2003b) which comprises 26 objects at z & 2:0 (excluding the sources with tentative redshifts
or complex/multiple structure or possible contamination: their Types s and m, respectively)
of which 20 are BLAGN, thus an optical type-2 QSO+AGN fraction of 23%. This may arise
from an observational selection as 10 (53%) of the 19 CDFS sources at z & 2, with secure
redshift identication, have R > 24 as compared to only 2 (8%) out of 26 CDFN sources.
The segregation between the X-ray type-1 and type-2 QSOs/AGNs seen in the R versus
z diagram (Figure 17) is far less pronounced in the K versus z diagram (Figure 18). This
is most likely due to the presence of dust in X-ray type-2 QSOs/AGNs associated with
the X-ray absorbing material which severely obscures the nuclear component, as well as an
increased contribution of the galaxy host light in the K-band relative to that of the AGN. The
X-ray and optical versus redshift diagrams (Figure 16, 17 and 18) strongly suggest that the
X-ray type-1 and type-2 populations cover roughly the same range of intrinsic luminosities
(see also Rosati et al. 2002; Mainieri et al. 2002).
13.2. X-ray and Optical Colours
A segregation of the X-ray type-1 and type-2 populations is also present in the R K
versus z diagram (see Figure 19), as rst outlined by Lehmann et al. (2001) and conrmed
by Mainieri et al. (2002). The deeper Chandra observations reveal many more X-ray type-
2 sources which have optical/near IR colours dominated by the host galaxy and most of
them cluster around the SED tracks of elliptical and Sbc galaxies at 0:5 < z < 1:0 (see
also Rosati et al. 2002). The X-ray type-1 population usually follows the evolutionary
track of an unreddened QSO, except nine AGNs/QSOs at z & 1, all with R K & 4. This
may be due to either an important contribution of the galaxy host light in the near IR
or obscuration by dust. Among these nine X-ray type-1 sources, the X-ray luminous, red
BLAGN at z = 1:616 (XID 67) was observed with HST/WFPC2 and is clearly resolved
with an elliptical morphology (Koekemoer et al. 2002). A substantial contribution of the
host galaxy could also account for the red colour of two BLAGN at z ' 1:62 (XID 46, 101).
Obscuration by dust associated with the X-ray aborbing material is more probable for the
remaining six X-ray type-1 sources, of which four belong to the HEX optical class and are
at 1:6 . z . 2:6 (XID 31, 117, 563, 901) and two belong to the LEX optical class and are
at z ' 1:0 (XID 18, 242).

{ 32 {
For a large fraction of the X-ray sources, there is a relationship between the hardness
ratio, HR, and the R K colour as shown in Figure 20. The bluer objects are X-ray type-1
QSOs, whereas the redder ones are mostly X-ray type-2 AGNs at z  0:5 to 1.0. However, the
redder objects (R K > 4) cover a wide range of HR values, as already noted by Franceschini
et al. (2002), and they comprise many X-ray type-1 AGNs, including the nine objects
discussed above, while most of the remaining X-ray type-1 are z < 1 objects of the optical
LEX class. To constrain the nature of the redder, X-ray type-1 AGNs requires to conduct an
X-ray spectral analysis (Chandra and XMM-Newton data) of these sources (Streblyanskaya,
Mainieri et al. in preparation), primarily those with secure redshifts, and to derive the
morphological properties of their host galaxies using the HST observations from the GOODS-
ACS Treasury program.
13.3. X-ray Selected Extremely Red Objects
The fraction of extremely red objects (EROs: R K > 5.0) among X-ray sources appears
to increase with decreasing optical ux as found for a subset of the CDFN X-ray sources
(Alexander et al. 2001) and for Lockman Hole (LH) sources detected by XMM-Newton
(Mainieri et al. 2002). We use the CDFS sample given in Table 5 to conrm this trend.
There are 151 X-ray sources with bright, R<24, counterparts observed in the R and K bands.
Five sources were not detected in the K band (K > 20.3), but the upper limits on their R K
colours are smaller than 5. The fraction of EROs in this bright optical sample is 10% (15
objects). The fainter optical sample is limited to 24  R < 26 to have meaningful R K
upper limits and it comprises 72 X-ray sources. Most of these faint objects do not have
spectroscopic redshifts. Thus, in cases of several possible counterparts, the brigthest of the
best centred counterparts was selected. To the 14 EROs with measured R K colours, should
be added the four objects detected in the K band only (R > 26.3), thus with R K & 6.0.
For the X-ray counterparts not detected in the K band, all those with 24  R < 25 have
R K upper limits smaller than 5, but among the 10 objects with 25  R < 26 only four
have R K .5.0. The remaining six objects have R K upper limits in the range 5.3 to 5.6,
but we will consider them as non-EROs in order to get a conservative value of the number
of EROs among the fainter optical sample. The ERO fraction in the R24 sample is thus
25%, or 2.5 times higher than for the R<24 sample.
Six of the optically bright CDFS EROs have redshift estimates (5 secure), all with
z  1 (0:3). One is an X-ray AGN-1 (LEX optical class), and ve are X-ray AGN-2 (LEX
or ABS class) thus with strong optical obscuration associated with X-ray absorption. The
other nine objects do not show any optical emission/absorption feature and all, but one, have

{ 33 {
HR < 0:2. If they were at z  1, they would have luminosities LX (0.5-10 keV)> 10 42 erg
s 1 . The fraction of hard X-ray sources among the optically bright ERO population is thus
40%. Higher redshift sources are present in the optically faint ERO sample. Among the six
objects with redshift estimates (4 secure), ve are at 1:6 . z . 3:7 of which three are X-ray
luminous QSOs. The fraction of hard X-ray, optically faint EROs is 50%, but if there were a
majority of high z sources, the bulk of this faint ERO population would be heavily absorbed
X-ray sources. A similar result was found for the LH sources (Mainieri et al. 2002). This
sample comprises 66 objects with measured R K colour (only 20 are fainter than R=24),
of which 18 are EROs. Five EROs (28%) are not detected in the hard band as compared to
27% and 22% for the CDFS optically bright and faint ERO samples, respectively. The X-ray
spectral analysis of the LH sources shows that all, but one, of the HR > 1:0 sources have
high intrinsic absorption: ten have absorbing column densities NH > 10 22 cm 2 and two,
without redshift identication, have lower limits (observer frame) of NH;min > 10 21:5 cm 2 .
Among the X-ray selected EROs, the dominant population appears to be fairly luminous,
absorbed X-ray sources, thus of the X-ray type-2 AGN class, at intermediate and high
redshifts. This is consistent with the small fraction (1.5-10%) of near-IR selected EROs
detected in X-ray (Cimatti et al. 2003). EROs belonging to other classes, elliptical galaxies
or dusty starbursts (Stevens et al. 2003), are also most probably present. Indeed, among
the optically faint EROs, there are a few sources with optically red and soft X-ray spectra
(e.g. XID 579b).
Objects of dierent classes are also found for EROs in the HDFN and the Lockman
hole (Franceschini et al. 2002; Stevens et al. 2003): sources at z  1 with SEDs typical of
elliptical galaxies, dusty starbursts and z > 1:5 absorbed AGN.
13.4. Luminosities
A trend of increasing hard X-ray luminosity (2-10 keV band) with absolute K magnitude
can be seen in Figure 21. This trend is not present when the X-ray luminosity in the broad
0.5-10 keV band is considered instead (see also Franceschini et al. 2002). We also show in
this gure the eect expected from the correlation found between the bulge luminosity and
the black hole mass (Marconi & Hunt 2003). We used very uncertain assumptions to derive
this curve. We assumed that around 40% of the K-band emission originates in the bulge
and we assumed that the X-ray luminosity is 0.1% of the Eddington limit luminosity. The
observed X-ray luminosity in the hard band is close to the intrinsic one (small K correction
for most of the sources) and the reddening correction for the K absolute magnitude is much
smaller in the near-IR than in the optical, although it could still be important for the

{ 34 {
extremely red objects. We thus expect a tighter correlation between the mid-IR luminosity,
to be obtained by the Spitzer-GOODS Legacy program, and the hard X-ray luminosity.
The trend present in Figure 21 reinforces the suggestion made above that the X-ray type-1
and type-2 populations cover the same range of luminosities, thus trace similar levels of
gravitational accretion. They dier by either the environment close to the AGN and/or the
viewing angle to the nucleus, the contribution of the light from an early-type host galaxy, or
the dust content and dust-to-gas ratio within the host galaxy, or an associated starburst.
The observed hard X-ray luminosity as a function of redshift is shown in Figure 22.
There are X-ray luminous X-ray type-1 QSOs down to z = 0:5, thus no strong evolution,
conrming the ndings in the CDFN (Barger et al. 2002). However, this only applies to
the X-ray type-1 population, as there is only one (8%) X-ray type-2 QSO (XID 51) out of
13 QSOs at 0:5 < z < 2. Two of the X-ray type-1 QSOs show narrow emission lines only
(XID 18, 31) and could be absorbed X-ray sources, as indeed conrmed by X-ray spectral
analysis of XID 31 (z = 1:603) which is an absorbed source with NH = 1:4  10 22 cm 2
(V. Mainieri, private communication). Even including these narrow-line QSOs in the type-2
sample would still lead to only 23% X-ray type-2 QSOs at lower redshift compared to 54% at
z > 2 (see Section 13.1). This dierence (detected at 90% condence level) would no longer
be as signicant if sources down to LX (2-10 keV) > 10 43:5 erg s 1 were considered instead.
Indeed, the ratio of X-ray type-2/type-1 sources at 0:5 < z < 2 increases with decreasing
hard X-ray luminosity, the type-2 population being dominant for LX (2-10 keV) < 10 43:0 erg
s 1 . This trend is conrmed by the analysis of the 2-10 keV luminosity function derived
from ASCA, HEAO1 and Chandra surveys (Ueda et al. 2003) which shows that, at z < 1,
the percentage of X-ray type-2 AGN (NH > 10 22 cm 2 ) decreases with increasing intrinsic
luminosity from 49% at LX (2-10 keV) = 10 43 erg s 1 to 26% at LX (2-10 keV) = 10 45 erg s 1 .
The X-ray spectral analysis (absorbing column densities and intrinsic X-ray luminosi-
ties) of the QSOs+AGNs of the CDFS and CDFN spectroscopic samples will enable the
determination of the cosmic evolution of the X-ray type-1 and the X-ray type-2/absorbed
sources, thus of a possible dierential cosmic evolution between these two populations. It
should be noted that Barger et al. (2002) mention the existence of only two type-2 QSOs
at 0:5 < z < 2 (both at z  1) while, in their Table 1, there are 12 broad-line QSO+AGN
sources in the same redshift range, which is consistent with our results. However, in the
CDFN, the fraction of type-2 QSOs is small at both intermediate and high (see Section
13.1) redshifts.

{ 35 {
14. SUMMARY AND OUTLOOK
We presented a catalog of 137 secure and 24 tentative spectroscopic identications of
the 349 X-ray objects (including 3 new, faint sources) in the CDFS eld, based on our
survey using the VLT. Our spectroscopic survey is 40% complete considering the whole
X-ray catalog, and 70% complete if we consider the subset in the central 8 0 radius with
optical counterparts at R<24. This can compared to the somewhat higher spectroscopic
completeness achieved in the Chandra Deep Field North identication programme (Barger et
al. 2002), where the corresponding fractions are 49% and 78%, respectively. Very recently,
optical identications have also been presented for the 2 Msec observation of the HDFN
(Barger et al. 2003b), which reach a completeness as high as 87% at R<24. At fainter
optical magnitudes (R>24), however, the fraction of reliable spectroscopic identications is
larger for the CDFS compared to the HDFN. This is becoming important in particular, when
comparing the fraction of X-ray type-2 QSOs at these faint magnitudes (see below).
We proposed a new, objective and simple scheme, based on X-ray luminosity and hard-
ness ratio, to classify objects into X-ray type-1 (unabsorbed) and X-ray type-2 (absorbed)
AGN. Hard (HR > 0:2) sources are classied as X-ray type-2 AGN or QSO, depending
on their X-ray luminosity. Soft sources (HR  0:2) are classied as X-ray galaxies, X-ray
type-1 AGN or QSO, depending on their X-ray luminosity. At high optical and X-ray lumi-
nosities, this classication scheme is largely coincident with the classical AGN classication
purely based on optical spectroscopic diagnostics. However, as soon as the integrated light
of the host galaxy becomes larger than the optical emission of the AGN nucleus, the optical
classication breaks down. Consequently, we are classifying many more objects as AGN,
than would be selected in optical samples. An additional advantage of our proposed classi-
cation scheme is that it only relies on X-ray uxes and redshift (to calculate LX ). So far we
only used optical spectroscopy to derive the redshift, but our scheme can use photometric
redshift techniques, thus going signicantly beyond the capabilities of optical spectroscopy.
Indeed, using photo-z techniques, more than 95% of the CDFS sources can be identied in
our scheme (Mainieri, private communication).
We have spectroscopically identied a sample of 8 secure and 2 tentative high-luminosity
X-ray sources with signicant absorption, our X-ray type-2 QSO class. Nine ( +4:1
3:0 : 1 errors)
of these sources are in the redshift range 2 < z < 4 and their optical spectra are dominated
by strong, narrow high excitation UV permitted lines, very similar to the prototypical object
CDFS-202 (Norman et al. 2002). In contrast, the spectroscopic sample existing in the HDFN
so far (Barger et al. 2002) only contains 2 ( +2:6
1:3 ) similar objects (HDFN #184 and #287).
This dierence may be due to the fact that our spectroscopy is pushing about one magnitude
deeper than the HDFN spectroscopy in a part of the eld. However, we can not exclude

{ 36 {
true cosmic eld-to-eld variations in the number of X-ray type-2 QSOs. The fraction of
X-ray type-2 to the total AGN population shows a signicant variation with observed X-ray
luminosity, consistent with, but even somewhat stronger than the trend found from ASCA
surveys in the 2-10 keV band (Ueda et al. 2003): the X-ray type-2 fraction decreases from
75 8% (8 type-1 vs. 24 type-2 AGN) in the luminosity range 10 42 43 erg s 1 , over 44 8%
(20 vs. 16 AGN) at luminosities 10 43 44 erg s 1 , to 33  10% (16 vs. 8) at 10 44 45 erg s 1
(see also Figure 13). This behaviour can probably explain some of the evolutionary trends
apparent in Figures 16 and 22.
We found spectroscopic evidence for two large-scale structures in the eld, predomi-
nantly populated by X-ray type-2 AGN but also X-ray type-1 AGN and normal galaxies:
one at z = 0:734 has a fairly narrow redshift distribution and comprises two clusters/groups
of galaxies centered on extended X-ray sources. The redshift distribution of the second one at
z = 0:674 is broader (velocity space) and traces a sheet-like structure. A detailed comparison
with the redshift spikes in a NIR-selected (K20) sample of galaxies in the same eld has been
performed by (Gilli et al. 2003). Similar, but much less pronounced redshift spikes have
also been observed in the HDFN at redshifts around z = 0:843 and z = 1:018 by (Barger et
al. 2002). AGN therefore trace large-scale structures as do normal galaxies. Further studies
on larger samples are required to investigate, whether AGN are more strongly clustered than
normal galaxies (Gilli et al. 2003) and, whether X-ray type-2 AGN are indeed clustering
stronger than X-ray type-1 AGN, as indicated by the CDFS results.
However, the objects in these spikes do not dominate the sample. The observed AGN
redshift distribution peaks at z  0:7, even if the objects in the spikes and also the normal,
starforming galaxies are removed. Compared to the pre-Chandra and XMM-Newton predic-
tions of population synthesis models of the X-ray background (Gilli et al. 2003), there is
an excess of z < 1 AGN, even taking into account the spectroscopic incompleteness of the
sample. These models will therefore have to be modied to incorporate dierent luminosity
functions and evolutionary scenarios for intermediate-redshift, lower-luminosity AGNs.
It will be interesting to study the correlation of active galaxies to eld galaxies in
the sheets and investigate the role that galaxy mergers play in the triggering of the AGN
activity. Finally, there may be a relation between the surprisingly low redshift of the bulk
of the Chandra sources, the existence of the sheets at the same redshift and the strongly
evolving population of dusty starburst galaxies inferred from the ISO mid-infrared surveys
(Franceschini et al. 2002).
The Chandra Deep Field South has been selected as one of the deep elds in the Spitzer
legacy programme Great Observatories Origins Deep Survey (GOODS). GOODS will pro-
duce the deepest observations with the Spitzer IRAC instrument at 3.6-8m and with the

{ 37 {
MIPS instrument at 24m over a signicant fraction of the CDFS (see Fosbury et al. 2001).
The same area has already been covered by an extensive set of pointings with the new Ad-
vanced Camera for Surveys (ACS) of the Hubble Space Telescope in BVIz to near HDF
depth. Following up the deep EIS survey in the CDFS, ESO has undertaken a large pro-
gram to image the GOODS area with the VLT to obtain deep JHKs images in some 32
ISAAC elds. A small spot inside the CDFS has also been selected as the location of the
HST ACS ultradeep eld (UDF), aiming at roughly two magnitudes fainter than the Hub-
ble Deep Fields, over a substantially larger area. An even larger eld than the CDFS has
been surveyed with the HST ACS program GEMS and has also been covered by multiband
optical photometry as part of the COMBO-17 survey (Wolf et al. 2003). The next step
in the optical identication and classication work is to use the extremely deep HST ACS
and VLT ISAAC (or EIS SOFI) data provided by GOODS and the narrow band photome-
try provided by COMBO-17 to obtain multicolour photometric redshifts for the objects not
covered by and/or too faint for our spectroscopic identication programme (Zheng et al., in
preparation).
Additional X-ray information in an area wider than the CDFS is existing from a deep
XMM-Newton pointing of 400 ksec exposure time (PI: Bergeron). The already existing
Chandra Megasecond coverage will be widened and deepened with four additional 250 ksec
ACIS-I pointings (PI: Brandt). The multiwavelength coverage of the eld is complemented
by deep 20 cm radio data from the VLA and ATCA. The CDFS will therefore ultimately be
one of the patches in the sky providing a combination of the widest and deepest coverage at
all wavelengths and thus a legacy for the future.
This publication makes use of data products from the Two Micron All Sky Survey,
which is a joint project of the University of Massachusetts and the Infrared Processing and
Analysis Center/California Institute of Technology, funded by the National Aeronautics and
Space Administration and the National Science Foundation. Three of our redshifts have
been obtained from the 2dFGRS public dataset.
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{ 42 {
Fig. 1.| X-ray ux in the 0.5-2 keV band versus R-band magnitude for the CDFS-sources
(larger symbols) and the ultradeep ROSAT survey in the Lockman Hole (smaller symbols).
Objects are marked according to their X-ray classication for the CDFS sources and the
original classication for the Lockman Hole sources: squares correspond to QSOs, circles to
AGN and triangles to galaxies. Type-1 and type-2 AGNs/QSOs have empty and solid sym-
bols, respectively. Stars are marked with star symbols. `X' symbols refer to spectroscopically
not securely identied CDFS counterpart candidates which we observed in our program, `+'
symbols mark objects we did not observe. The solid lines correspond to an X-ray to optical
ux ratio index (as discussed in Section 3) of 1, 0 and 0.4.

{ 43 {
20 22 24 26
0
10
20
30
Fig. 2.| The R-band magnitude distribution of the selected (primary) optical counterparts
of the X-ray sources in our survey (solid line). For comparision, we also show (dotted line)
the expected distribution of random eld galaxies normalized to the total area of the error
circles of our X-ray sources, based on galaxy number count measurements (Metcalfe et al.
2001; Jones et al. 1991).

{ 44 {
6000 7000 8000 9000
1
2
3
4
5
Fig. 3.| Flux calibrated spectra of a spectrophotometric standard star, Feige110 (Hamuy
et al. 1992, 1994; Oke 1990). The dashed line is the measured ux without removing the
second order contamination, solid line is the spectra after the correction. Empty squares are
the real ux values from literature.
.

{ 45 {
0.4 0.7
0.3 0.8
0.3 0.6
0.2 0.7
Fig. 4.| Comparing calculated LX values in dierent cosmologies. Plotted are the changes
as a function of redshift, compared to the
current
m =
0:3,
 = 0:7, H 0 = 70km s 1 Mpc 1
cosmology. Dotted lines are slight variations on the two basic parameters, without chang-
ing the Hubble constant. The solid line is the now
obsolete
m =
1,
 = 0, H 0 =
50km s 1 Mpc 1 cosmology. The result of an approximate formula (Pen 1999)
for
m = 0:3,

 = 0:7, H 0 = 70km s 1 Mpc 1 is also shown (dashed line).
.

{ 46 {
Fig. 5.| For these gures, see http://www.mpe.mpg.de/CDFS. Finding charts and VLT
spectra of CDFS sources. Images are based on our FORS R-band imaging. The circles
indicate the positional error (Giacconi et al. 2002). The images are 20 00  20 00 in size. If
multiple optical counterparts were considered, they are marked on the nding charts. Next
to the nding charts we show all spectroscopic observations available for the object. On the
horizontal axis both the observed (bottom) and rest frame (top { if available) wavelength
is shown in  A units. The vertical axis is the measured ux, f  in 10 18 erg cm 2 s 1  A 1
units. Important emission (above the spectra) and absorption (below the spectra) features
used for identication are also marked.

{ 47 {
Fig. 6.| For this gure, see http://www.mpe.mpg.de/CDFS/. Extended object 138. The
image covers 60  60 arcsec.

{ 48 {
Fig. 7.| For this gure, see http://www.mpe.mpg.de/CDFS/. Extended object 249. The
image covers 60  60 arcsec.

{ 49 {
Fig. 8.| For this gure, see http://www.mpe.mpg.de/CDFS/. Extended object 560. The
image covers 60  60 arcsec.

{ 50 {
Fig. 9.| For this gure, see http://www.mpe.mpg.de/CDFS/. Extended object 566. The
image covers 60  60 arcsec.

{ 51 {
Fig. 10.| For this gure, see http://www.mpe.mpg.de/CDFS/. Extended object 594. The
image covers 60  60 arcsec.

{ 52 {
Fig. 11.| For this gure, see http://www.mpe.mpg.de/CDFS/. Extended object 645. The
image covers 60  60 arcsec.

{ 53 {
0 1 2 3 4 5 6
­1
0
1
Fig. 12.| Hardness ratio versus redhsift, assuming a typical absorbed AGN spectrum with
= 2 and dierent absorptions, expressed as log(NH ). Identied CDFS objects are also
plotted (see Figure 1 for symbols). HEX objects (likely optical type-2 AGNs) are additionaly
marked with a hexagon.

{ 54 {
Fig. 13.| Hardness ratio versus observed X-ray luminosity in the 0.5-10 keV band. Symbols
in the left panel show the classical optical classication (empty squares: BLAGN, lled
squares: HEX, diamonds: LEX, triangles: ABS). Symbols in the right panel are as in see
Figure 1 and follow the X-ray classication presented in Section 7. The BAL QSO (XID 62)
is also marked.

{ 55 {
Fig. 14.| Spatial distribution of the X-ray sources with and without pectroscopic observa-
tions. Object classes are marked as in Figure 1. The area covered by our spectroscopic masks
(solid line), the imaging survey (long dashed line), the K20 survey area (short dashed line)
and an 8 arcmin radius circle, centered on the nominal CDFS pointing (3:32:28.0 -27:48:30
J2000; dotted line) is also shown.

{ 56 {
Fig. 15.| Redshift distribution of the various classes of X-ray sources as well as their
cumulative distribution. Object XID 138a and 138b are counted as two separate objects.
The 4 extended objects (249, 566, 594 and 645) are not included. Two bin sizes (
z = 0.01
and 0.1) are selected to show the excess of objects around z = 0:674 and 0.734.

{ 57 {
Fig. 16.| X-ray ux of the CDFS sources as a function of redshift for the 0.5-2 keV band
(top) and 2-10 keV band (bottom). Symbols are as in Figure 1.

{ 58 {
Fig. 17.| R magnitude as a function of redshift for the CDFS X-ray sources. Symbols are
as in Figure 1. The dotted lines indicate the two structures around z = 0:67 and 0.73. The
solid line corresponds to an absolute magnitude of MR = 23.

{ 59 {
Fig. 18.| K magnitude as a function of redshift. Symbols are as in Figure 1. The solid line
corresponds to an absolute magnitude of MK = 26. The brigthest source (in both the K-
and R-bands) at z > 1:5 is the BAL QSO at z = 2:810 (XID 62).

{ 60 {
Fig. 19.| R K colour as a function of redshift. Symbols are as in Figure 1. The ve evolu-
tionary tracks correspond to an unreddened QSO, with L = L ?
B , and unreddened elliptical,
Sbc, Scd and irregular L ? galaxies from the Coleman et al. (1980) SED templates.

{ 61 {
Fig. 20.| The hardness ratio (dened from the net count rates in the 2-10 keV and 0.5-2
keV bands: see Section 7) versus R K colour. Symbols are as in Figure 1 for the reliable z
identications, similar symbols but of smaller sizes for the tentative z identications.

{ 62 {
Fig. 21.| The X-ray luminosity in the 2-10 keV band versus the absolute K magnitude.
Symbols are as in Figure 1. We also convert the relation found between bulge luminosity
and black hole mass (Marconi & Hunt 2003), by assuming that around 40% of the K-band
emission is coming from the bulge and an X-ray luminosity of 0.1% of the Eddington limit
(Solid line).

{ 63 {
Fig. 22.| The X-ray luminosity in the 2-10 keV band versus redshift. Symbols are as in
Figure 1.

{ 64 {
Fig. 23.| For these gures, see http://www.mpe.mpg.de/CDFS/. Finding charts and VLT
spectra of the eld sources. Images are based on our FORS R-band imaging. The images are
20 00  20 00 in size. Next to the nding charts we show all spectroscopic observations available
for the object. On the horizontal axis both the observed (bottom) and rest frame (top { if
available) wavelength is shown in  A units. The vertical axis is the measured ux, f  in 10 18
erg cm 2 s 1  A 1 units. Important emission (above the spectra) and absorption (below the
spectra) features used for identication are also marked.

{ 65 {
Table 1. X-ray sources not yet published in Giacconi et al. (2002).
XID a CXO CDFS b RA (J2000) c Dec (J2000) d Soft Cts. e Hard Cts. f Exp Time g Soft Flux h Error i Hard Flux j Error k HR l
901 J033235.8-274917 03 32 35.78 -27 49 16.82 11.05.0 <9.0 828.4(857.7) 6.1e-17 2.9e-17 <3.1e-16 -1
902 J033222.1-275113 03 32 22.08 -27 51 13.05 <7.0 12.16.2 792.3(804.1) <3.9e-17 { 4.5e-16 2.0E-16 +1
903 J033226.0-274049 03 32 25.97 -27 40 49.21 22.510.4 <3 824.3(820.2) 1.3e-16 0.6e-16 < 1e-16 -1
a Unique Detection ID
b IAU Registered Name, based on X{ray coordinates
c Right Ascension
d Declination
e Net Counts in soft (0.5 - 2 keV) band
f Net Counts in hard (2 - 10 keV) band
g Eective exposure time in the soft(hard) band, in kiloseconds
h Flux in soft (0.5 - 2 keV) band, c.g.s. units
i Error on soft ux
j Flux in hard (2 - 10 keV) band, c.g.s. units
k Error on hard ux
l Hardness Ratio, dened as (H - S)/(H + S) where H and S are the net counts in the hard and soft bands respectively

{ 66 {
Table 2. X-ray-to-optical ux ratio ranges for dierent classes of objects
Object class log(f 0:3:::3:5 =f V ) f X -shift V-R log(f 0:5:::2:0 =f R )
AGN 1.0. . . +1.2 0.25. . . 0.33 0.0. . . 1.0 1.4. . . +1.1
BL Lac +0.3. . . +1.7 0.25. . . 0.33 0.0. . . 1.0 0.1. . . +1.6
Clusters 0.5. . . +1.5 0.18. . . 0.25 0.1. . . 0.4 0.6. . . +1.6
Galaxies 1.8. . . 0.2 0.10. . . 0.30 0.1. . . 1.0 2.2. . . +0.0
M stars 3.1. . . 0.5 0.05. . . 0.20 0.6. . . 1.0 3.4. . . 0.4
K stars 4.0. . . 1.5 0.05. . . 0.20 0.4. . . 0.6 4.1. . . 1.3
G stars 4.3. . . 2.4 0.05. . . 0.20 0.3. . . 0.5 4.4. . . 2.2
B-F stars 4.6. . . 3.0 0.05. . . 0.20 -0.5. . . 0.3 4.6. . . 2.5
Note. | The typical X-ray-to-optical ux ratios in our new bands (0.5. . . 2 keV in
X-ray, R-band in optical) as derived from the previously determined values (Stocke
et al. 1991). The f X -shift is the typical shift of X-ray ux (in log 10 units) due to
the narrower energy range, assuming typical X-ray spectra for the class of objects.
V-R is the typical optical color range in the class. The last column includes our new
normalization of the X-ray-to-optical ux ratio, as discussed in the text (Section 3).
In the case of clusters, the magnitude refers to the brigtest cluster galaxy (BCG).

{ 67 {
Table 3. The location of lines in second order diraction
Line Position 1 Flux 1 FWHM 1 Position 2 Flux 2 FWHM 2 Filter
(  A) (  A) (ADU) (  A) (  A) (ADU) (  A) (Bessel)
3888.6 3887 13847 26 7462 3632 30 U
3650.1 3648 90265 30 6954 36364 35 U
3650.1 3649 17119 27 6957 8380 34 B
3888.6 3888 79904 27 7465 19142 30 B
4046.6 4047 346283 30 7801 44653 30 B
4358.3 4359 795630 28 8457 51040 30 B
4471.5 4472 97692 27 8694 5151 30 B
5015.7 5014 172340 28 9878 1946 33 V
Note. | The location, apparent width and apparent strength of selected arc lines in rst and
second order diraction in FORS, using the 150I grism. Flux values are in instrumental counts
(ADU). The Filter column indicates which (Bessel) lters we used for the particular line. The
observed location of the rst order diraction was used to test that the lters do not introduce
signicant shifts in our wavelength solution.

{ 68 {
Table 4. Summary of spectroscopic observations.
Mask Exposure Slit seeing Slitloss Night
(s) (arcsec) (arcsec) %
6+7 31800, 31800 1.2 0.8/0.6 40 2000 Oct 27-28
15 41800+1300 1.2 0.7/0.8 45 2000 Oct 27-28
22+23+24 31800, 1800, 21800 1.2 1.0/0.9 50 2000 Oct 28-29
28+29 21800, 31800 1.2 0.6/0.9 40 2000 Oct 28-29
36+39+40 1800, 1800, 41800 1.2 1.3/0.6 65 2000 Oct 29-30
46+47 41800, 1800+900 1.2 0.5/0.7 35 2000 Oct 29-30
78 61800+945 1.2 0.5/0.6 N/A 2000 Nov 24-25
82 51800 1.2 0.6/0.6 35 2000 Nov 23-24
84 61800 1.2 0.9/0.8 45 2000 Nov 23-24
86 31800+1535 1.2 1.1/1.0 40 2000 Nov 24-25
88 1200 1.2 0.8/0.6 80 2000 Nov 23-24
89 1200 1.2 0.8/0.6 75 2000 Nov 23-24
90 1200 1.2 1.3/1.1 90 2000 Nov 23-24
99 1800 1.2 0.9/1.3 50 2000 Nov 24-25
119+120+121 2700, 22700, 22700+3600 1.0 0.5/0.7 70 2001 Sep 20-21
122 42700 1.0 0.6/0.8 70 2001 Sep 18-19
134 2500+2700 1.4 0.9/0.8 70 2001 Sep 17-18, 19-20
137 1800+2700 1.4 1.0/1.0 60 2001 Sep 18-19, 19-20
138+139 31800, 22700 1.0 0.5/0.6 55 2001 Sep 17-18
146 32700 1.4 0.7/0.9 60 2001 Sep 19-20
MXU2.1 91800+2400 1.0 0.7/0.9 N/A 2001 Nov 13-14, 14-15
MXU4.1 121800+1134 1.0 0.9/0.8 N/A 2001 Nov 12-13
MXU5.1 41800 1.0 0.5/0.7 70 2001 Nov 14-15
MXU11.1 91800+2400 1.0 0.6/0.8 sl 2001 Nov 13-14
MOS11.1 41800 ?.? 1.2/1.0 75? 2001 Nov 11-12
MXU1.1 22100 ?.? 0.5/0.7 sl 2001 Dec 18-19
Note. | Seeing values refer to seeing directly measured on the acquisition image (rst value) and the seeing
measured by the DIMM seeing monitor during the observations (second number). The slitloss is estimated
from relatively bright point sources (if observed) by comparing synthetic magnitudes calculated from the ux
calibrated spectra and broad-band magnitudes. This value is only to be used to asses the overall quality of
each mask as it does not take into account the extend and centering of individual objects (see Section 6.3).

{ 69 {
Table
5.
Optical
spectroscopy
results.
No
mask

ô
R
R
K
LX
HR
z
Class
Class
Qual
Comments
(J2000)
(J2000)
(mag)
(mag)
log
erg s


(opt)
(X-ray)
1a
36
03:33:09.49
27:46:03.6
20.12
NA
42.5
0.18
0.347
LEX
AGN-2
0.5
6650 A-
1b
39
03:33:09.65
27:46:04.0
21.74
NA
43.6
0.18
1.015
LEX
AGN-2
1.0
6700 A-
4a
36+39+40
03:33:03.63
27:45:18.9
22.80
3.19
43.9
0.48
1.260
BLAGN
AGN-1
1.0
4650 A-,
Mg
II
6a
36+39+40
03:33:02.69
27:48:23.5
23.67
4.17
0.52
-
0.0
4500 A-
10
36
03:32:59.77
27:46:26.4
20.69
3.94
42.8
0.16
0.424
LEX
AGN-2
2.0+
11
36+39+40
03:32:59.83
27:47:48.2
21.83
2.73
45.0
0.51
2.579
BLAGN
QSO-1
2.0+
C
IV
12
137
03:32:59.69
27:50:30.4
19.89
3.32
42.2
0.50
0.251
ABS
AGN-1
2.0+
-9400 A
13
36
03:32:59.09
27:43:39.5
20.93
3.71
43.6
0.46
0.733
BLAGN
AGN-1
2.0+
Mg
II,
[O
II]
15
15
03:32:52.88
27:51:20.0
22.62
4.09
0.45
-
0.0
6700 A-
15
137
03:32:52.88
27:51:20.0
22.62
4.09
43.9
0.45
1.227
BLAGN
AGN-1
1.0
Mg
II
17c
15
03:32:49.11
27:55:06.5
24.62
4.23
0.41
-
0.0
18
146
03:32:47.90
27:42:32.8
21.28
4.21
44.3
0.21
0.979
LEX
QSO-1
2.0+
19
47
03:32:47.92
27:41:48.0
21.76
3.95
43.8
0.46
0.740
BLAGN
AGN-1
2.0+
[NeV]?,
Mg
II
19
84
03:32:47.92
27:41:48.0
21.76
3.95
43.8
0.46
0.733
BLAGN
AGN-1
2.0+
[NeV]?,
[O
II],
Mg
II
20a
86
03:32:44.46
27:49:40.3
23.99
4.76
43.4
0.12
1.016
LEX
AGN-2
2.0+
3600 A-
20a
137
03:32:44.46
27:49:40.3
23.99
4.76
43.4
0.12
1.016
LEX
AGN-2
2.0+
5400 A-
21
15
03:32:44.32
27:52:51.3
23.96
<3.66
44.2
0.58
3.476
BLAGN
QSO-1
2.0+
C
IV
21
137
03:32:44.32
27:52:51.3
23.96
<3.66
44.2
0.58
3.471
BLAGN
QSO-1
2.0+
3950
A-,C
IV
22
15
03:32:43.24
27:49:14.2
22.59
3.11
44.4
0.51
1.92
BLAGN
QSO-1
2.0+
5000 A-,
Mg
II
23
84
03:32:41.87
27:44:00.2
24.93
<4.63
0.46
-
0.0
24
15
03:32:41.86
27:52:02.6
22.58
3.59
44.8
0.36
3.592
BLAGN
QSO-1
2.0+
C
IV,
[N
IV],
associated
absorption
system
24
137
03:32:41.86
27:52:02.6
22.58
3.59
44.8
0.36
3.610
BLAGN
QSO-1
2.0+
C
IV,
[N
IV],
associated
absorption
system
25
15
03:32:40.85
27:55:47.0
24.64
5.95
43.1
0.35
0.625
ABS
AGN-2
0.5
26
134
03:32:39.71
27:46:11.1
24.55
5.04
0.23
-
0.0
26
146
03:32:39.71
27:46:11.1
24.55
5.04
0.23
-
0.0
27
MXU2.1
03:32:39.67
27:48:50.5
24.54
4.76
44.7
0.16
3.064
HEX
QSO-2
2.0+
CIV
28
86
03:32:39.09
27:46:02.0
20.85
2.70
43.5
0.20
1.216
BLAGN
AGN-1
2.0+
-8950 A,
Mg
II
30a
28+29
03:32:38.13
27:39:45.0
20.42
2.37
44.1
0.53
0.837
BLAGN
QSO-1
2.0+
Mg
II,
H
,
H ,
[O
II],
[Ne
V]
31
15
03:32:37.78
27:52:12.4
24.57
5.88
44.4
0.52
1.603
HEX
QSO-1
2.0+
HeII,
C
IV,
absorbed
below
2
keV
32
28+29
03:32:37.47
27:40:00.3
22.36
3.74
43.1
0.49
0.664
BLAGN
AGN-1
2.0+
broad
H
,
[NeV]
33
03:32:36.79
27:44:07.2
22.52
4.06
43.4
0.40
0.665
LEX
AGN-1
2.0+
[O
II]
ref
1
34a
15
03:32:34.96
27:55:11.2
22.86
4.15
43.3
0.32
0.839
HEX
AGN-1
2.0+
-8400 A,
[NeV]
36a
138+139
03:32:33.02
27:45:47.6
23.38
6.02
0.37
-
0.0
or
arms

{ 70 {
Table
5|Continued
No
mask

ô
R
R
K
LX
HR
z
Class
Class
Qual
Comments
(J2000)
(J2000)
(mag)
(mag)
log
erg s


(opt)
(X-ray)
36b
138+139
03:32:32.97
27:45:45.8
20.82
3.86
0.37
-
0.0
6550 A-
37*
46+47
03:32:32.09
27:41:55.3
23.39
3.59
0.23
-
0.0
4400 A-
37*
84
03:32:32.09
27:41:55.3
23.39
3.59
0.23
-
0.0
37*
146
03:32:32.09
27:41:55.3
23.39
3.59
0.23
-
0.0
38
03:32:30.30
27:45:05.4
22.10
3.14
43.5
0.56
0.738
BLAGN
AGN-1
2.0+
Mg
II,
H
,
[O
III],
ref
1
39
03:32:30.06
27:45:30.7
21.02
2.92
44.3
0.47
1.218
BLAGN
QSO-1
2.0+
Mg
II,
[Ne
V],
ref
2
41
22
03:32:27.62
27:41:45.0
22.24
4.14
43.2
0.52
0.667
HEX
AGN-2
2.0+
H
,
[NeV]?
41
84
03:32:27.62
27:41:45.0
22.24
4.14
43.3
0.52
0.668
HEX
AGN-2
2.0+
H
,
[NeV],
line
ratios
42a
28
03:32:27.00
27:41:05.1
19.04
2.77
44.5
0.54
0.734
BLAGN
QSO-1
2.0+
Mg
II,
[O
III]
43
23+24
03:32:26.76
27:41:45.6
22.61
4.58
43.0
0.06
0.737
LEX
AGN-2
2.0+
5500 A-
43
84
03:32:26.76
27:41:45.6
22.61
4.58
43.0
0.06
0.734
LEX
AGN-2
2.0+
44a
28
03:32:26.49
27:40:35.7
19.79
2.52
44.2
0.63
1.031
BLAGN
QSO-1
2.0+
Mg
II,
H
,
[Ne
V]
45
82
03:32:25.69
27:43:05.8
25.35
5.12
0.16
-
0.0
5000 A-
45
84
03:32:25.68
27:43:05.7
25.35
5.12
44.4
0.16
2.291
LEX
QSO-2
1.0
46
82
03:32:25.16
27:42:18.9
23.01
4.68
44.0
0.57
1.617
BLAGN
QSO-1
2.0+
4000 A-,
C
IV,
Mg
II
47
139
03:32:24.97
27:41:01.6
21.98
4.04
43.0
0.44
0.733
LEX
AGN-2
2.0+
6100 A-
49
22+23+24
03:32:24.25
27:41:26.5
20.99
4.03
42.8
0.47
0.534
LEX
AGN-1
2.0+
4600 A-
50
119+120+121
03:32:19.00
27:47:55.4
24.14
2.38
42.7
0.03
0.670
ABS
AGN-2
1.0
50
138+139
03:32:19.00
27:47:55.4
24.14
2.38
0.03
-
0.0
50
MXU1.1
03:32:19.05
27:47:55.4
24.14
2.38
0.03
-
0.0
51a
6+7
03:32:17.18
27:52:20.8
23.22
4.98
44.0
0.61
1.097
LEX
QSO-2
2.0+
52
82
03:32:17.15
27:43:03.4
21.04
3.55
43.2
0.55
0.569
BLAGN
AGN-1
2.0+
Mg
II,
[O
III]
53
78
03:32:14.99
27:51:27.2
21.59
4.30
43.0
0.45
0.668
LEX
AGN-1
2.0+
53
119+120+121
03:32:14.99
27:51:27.2
21.59
4.30
43.0
0.45
0.675
BLAGN
AGN-1
2.0+
-9500 A,
Mg
II
54
122
03:32:14.61
27:54:20.7
25.69
<5.39
44.3
0.07
2.561
HEX
QSO-2
2.0+
C
IV
55
6
03:32:14.02
27:51:00.9
22.53
4.06
41.5
0.25
0.122
HEX
AGN-2
2.0+
H,
[FeVII],
low
LX
AGN-2
56a
23
03:32:13.24
27:42:41.1
20.18
3.54
43.5
0.11
0.605
HEX
AGN-2
2.0+
H
,
[NeV]
57
122
03:32:12.96
27:52:36.9
24.04
3.23
44.5
0.02
2.562
HEX
QSO-2
2.0+
C
IV,
He
II
59
78
03:32:11.33
27:52:13.7
26.47
<6.17
0.21
-
0.0
59
MXU4.1
03:32:11.34
27:52:13.7
26.47
<6.17
0.21
-
0.0
60
22+23+24
03:32:10.92
27:44:15.2
22.51
3.33
44.5
0.49
1.60
BLAGN
QSO-1
2.0+
C
IV,
Mg
II
60
82
03:32:10.92
27:44:15.2
22.51
3.33
44.5
0.49
1.615
BLAGN
QSO-1
2.0+
3600 A-,
C
IV,
Mg
II
61
22+23+24
03:32:10.47
27:43:09.1
23.98
5.80
0.45
-
0.0
nearby
bright
star
62
6+7
03:32:09.46
27:48:06.8
20.39
2.58
44.6
0.07
2.810
BLAGN
QSO-2
2.0+
BAL
QSO,
C
IV,
[O
III]

{ 71 {
Table
5|Continued
No
mask

ô
R
R
K
LX
HR
z
Class
Class
Qual
Comments
(J2000)
(J2000)
(mag)
(mag)
log
erg s


(opt)
(X-ray)
63
22+23+24
03:32:08.68
27:47:34.4
18.50
2.78
44.2
0.52
0.544
BLAGN
QSO-1
2.0+
Mg
II,
H
,
[Ne
V]
63
88
03:32:08.68
27:47:34.4
18.50
2.78
44.1
0.52
0.543
BLAGN
QSO-1
2.0+
-8850 A,
Mg
II,
H
,
[NeV]
64
139
03:32:08.01
27:46:57.3
24.77
<4.47
0.34
-
0.0
65
MOS11.1
03:32:03.86
27:53:29.8
-
K20.34
0.48
-
0.0
66
22
03:32:03.67
27:46:03.8
20.72
4.10
43.2
0.55
0.574
LEX
AGN-2
2.0+
-8700 A
67
82
03:32:02.47
27:46:00.4
23.56
4.63
44.4
0.41
1.616
BLAGN
QSO-1
2.0+
4200 A-,
Mg
II
68
22+23+24
03:32:01.58
27:43:27.0
22.83
2.11
44.7
0.42
2.726
BLAGN
QSO-1
2.0+
-7700 A,
C
IV
70a
22+23+24
03:32:01.53
27:46:46.8
23.62
5.67
0.47
-
0.0
-8000 A
71
82
03:32:00.35
27:43:19.6
22.10
2.95
43.8
0.44
1.037
BLAGN
AGN-1
2.0+
Mg
II,
[Ne
V]
73
MXU11.1
03:31:58.12
27:48:34.0
22.14
4.42
43.2
0.34
0.734
LEX
AGN-1
2.0+
73
MOS11.1
03:31:58.02
27:48:34.7
22.14
4.42
43.2
0.34
0.734
LEX
AGN-1
2.0+
75
MXU11.1
03:31:55.38
27:54:48.4
20.75
3.99
43.7
0.29
0.737
HEX
AGN-2
2.0+
[NeV],
4200A-
75
MOS11.1
03:31:55.38
27:54:48.4
20.75
3.99
43.7
0.29
0.737
HEX
AGN-2
2.0+
[NeV],
line
ratios
76
MOS11.1
03:31:52.49
27:50:17.6
24.50
4.64
44.6
0.07
2.394
LEX
QSO-2
1.0
77
36+39+40
03:33:01.54
27:45:42.6
20.63
3.83
42.8
0.48
0.622
BLAGN
AGN-1
2.0+
3950 A-,
Mg
II,
[O
II]
78
22+23+24
03:32:30.06
27:45:23.6
22.44
4.07
43.4
0.54
0.960
LEX
AGN-1
1.0
7000 A-
78
84
03:32:30.06
27:45:23.6
22.44
4.07
43.4
0.54
0.960
BLAGN
AGN-1
2.0+
4200 A-,
Mg
II,
[O
II]
79
84
03:32:37.99
27:46:26.3
26.55
6.04
0.42
-
0.0
6000 A-
79
MXU2.1
03:32:38.02
27:46:26.4
26.55
6.04
0.42
-
0.0
80
78
03:32:10.92
27:48:57.0
24.63
4.36
0.52
-
0.0
80
119+120+121
03:32:10.93
27:48:57.3
24.63
4.36
0.52
-
0.0
81
138+139
03:32:25.95
27:45:14.4
26.04
<5.74
0.44
-
0.0
82a
122
03:32:14.86
27:51:04.0
-
K19.00
0.01
-
0.0
82b
78
03:32:15.08
27:51:04.6
25.94
<5.64
0.01
-
0.0
83
22+23+24
03:32:14.98
27:42:24.9
23.08
5.81
0.23
-
0.0
83
139
03:32:14.98
27:42:24.9
23.08
5.81
0.23
-
0.0
83
MXU5.1
03:32:14.98
27:42:24.9
23.08
5.81
0.23
-
0.0
84
03:32:46.77
27:42:12.2
16.03
2.88
40.7
0.68
0.103
ABS
gal
2.0+
2dF
TGS243Z005
85
15
03:32:44.60
27:48:35.9
24.78
3.30
0.39
-
0.0
5850 A-
85
MXU2.1
03:32:44.60
27:48:35.9
24.78
3.30
44.0
0.39
2.593
LEX
QSO-1
1.0
86a
84
03:32:33.85
27:45:20.7
24.65
3.27
0.05
-
0.0
4200 A-
86a
134
03:32:33.84
27:45:20.6
24.65
3.27
0.05
-
0.0
87
6+7
03:32:18.25
27:52:41.4
23.98
2.73
43.3
1.00
2.801
BLAGN
AGN-1
2.0+
C
IV
89
22+23+24
03:32:08.28
27:41:53.6
24.58
<4.28
43.9
0.44
2.47
BLAGN
AGN-1
2.0+
C
IV

{ 72 {
Table
5|Continued
No
mask

ô
R
R
K
LX
HR
z
Class
Class
Qual
Comments
(J2000)
(J2000)
(mag)
(mag)
log
erg s


(opt)
(X-ray)
90
03:32:42.12
27:57:04.1
13.82X
3.60
0.87
0
M-star
M-star
2.0+
ref
3
91
86
03:32:42.84
27:47:02.6
24.10
<3.80
44.4
0.31
3.193
BLAGN
QSO-1
1.0
C
IV
92
03:32:49.65
27:54:53.9
16.91
2.80
0.71
0
star
star
2.0+
ref
3
93
78
03:32:02.34
27:52:34.0
23.67
4.04
0.42
-
0.0
contamination,
4000 A-
94a
39+40
03:32:44.00
27:46:33.5
24.72
<4.42
1.00
-
0.0
-8600 A
94a
86
03:32:44.00
27:46:34.0
24.72
<4.42
1.00
-
0.0
contamination
94b
84
03:32:43.98
27:46:32.7
24.50
<4.20
1.00
-
0.0
6000 A-
94c
39+40
03:32:44.00
27:46:35.1
24.83
<4.53
43.5
1.00
2.688
LEX
AGN-1
0.5
-8600 A
94c
146
03:32:44.01
27:46:35.1
24.83
<4.53
1.00
-
0.0
4600 A-
95
03:32:29.92
27:44:25.2
16.49
2.44
40.3
0.70
0.076
LEX
gal
2.0+
ref
2
96a
78
03:32:20.92
27:52:22.6
24.85
<4.55
0.39
-
0.0
97a
22+23+24
03:32:10.99
27:40:53.7
23.56
3.45
0.40
-
0.0
97b
22+23+24
03:32:11.09
27:40:56.1
19.56
2.36
41.7
0.40
0.181
LEX
gal
2.0
not
centered
98a
137
03:32:44.28
27:51:41.2
19.75
3.64
41.0
1.00
0.279
HEX
gal
2.0+
H,
H
,
[NeV],
interacting,
possible
low
LX
AGN-1
98b
137
03:32:44.06
27:51:43.3
19.19
4.00
41.0
1.00
0.279
ABS
gal
1.0
interacting
99
MOS11.1
03:32:05.11
27:53:55.1
25.22
5.65
0.32
-
0.0
100
86
03:32:35.98
27:48:50.4
22.00
2.97
42.3
1.00
1.309
LEX
AGN-1
1.0
101a
86
03:32:55.60
27:47:51.9
24.69
3.97
0.43
-
0.0
4300 A-
101a
MXU2.1
03:32:55.50
27:47:51.9
24.69
3.97
43.6
0.43
1.625
BLAGN
AGN-1
2.0+
C
IV,
Mg
II
103
03:32:28.90
27:43:56.2
18.19X
2.96
41.3
0.69
0.215
ABS
gal
2.0+
ref
2
108a
82
03:32:05.78
27:44:47.2
25.94
<5.64
0.36
-
0.0
108b
82
03:32:05.72
27:44:48.2
26.36
<6.06
0.36
-
0.0
110
86
03:32:58.61
27:46:32.0
23.25
<2.95
42.4
0.21
0.622
LEX
AGN-1
1.0
110
MXU2.1
03:32:58.61
27:46:32.0
23.25
<2.95
42.4
0.21
0.622
LEX
AGN-1
2.0+
112a
MXU11.1
03:31:51.94
27:53:27.4
24.83
<4.53
44.3
0.20
2.940
HEX
QSO-2
2.0+
HeII,
NV,
OVI
114
78
03:32:07.63
27:52:13.7
24.52
4.92
0.05
-
0.0
114
122
03:32:07.63
27:52:13.7
24.52
4.92
0.05
-
0.0
-8550 A
114
MXU4.1
03:32:07.63
27:52:13.7
24.52
4.92
0.05
-
0.0
116*
03:32:30.07
27:44:05.4
16.97
2.55
40.3
0.56
0.076
LEX
gal
2.0+
ref
2
117
82
03:32:03.05
27:44:50.2
25.47
4.97
44.0
0.53
2.573
HEX
QSO-1
2.0+
CIV
121
MXU11.1
03:31:51.16
27:50:51.6
22.44
4.14
42.7
0.11
0.674
LEX
AGN-2
2.0+
122
86
03:32:57.60
27:45:48.6
23.14
<2.84
0.21
-
0.0
124a
82
03:32:02.47
27:45:24.2
25.29
<4.99
1.00
-
0.0
124b
22+23+24
03:32:02.44
27:45:25.9
24.94
<4.64
1.00
-
0.0

{ 73 {
Table
5|Continued
No
mask

ô
R
R
K
LX
HR
z
Class
Class
Qual
Comments
(J2000)
(J2000)
(mag)
(mag)
log
erg s


(opt)
(X-ray)
124b
82
03:32:02.43
27:45:25.8
24.94
<4.64
1.00
-
0.0
132*
15
03:32:44.01
27:54:54.1
24.89
<4.59
42.8
0.05
0.908
LEX
AGN-2
1.0
138a*
46
03:32:50.11
27:41:34.8
22.22
4.42
42.6
1.00
0.972
BLAGN
AGN-1
2.0+
Mg
II,
[O
II],
interacting
138b*
47
03:32:50.01
27:41:35.8
22.68
2.65
42.6
1.00
0.967
LEX
AGN-1
2.0+
145
6+7
03:32:22.54
27:46:03.9
24.78
4.72
0.27
-
0.0
6950 A-
145
84
03:32:22.54
27:46:03.9
24.78
4.72
0.27
-
0.0
145
119+120+121
03:32:22.54
27:46:03.9
24.78
4.72
0.27
-
0.0
6400 A-
147*
84
03:32:46.34
27:46:32.1
25.14
5.09
0.65
-
0.0
6200 A-
147*
86
03:32:46.34
27:46:32.1
25.14
5.09
0.65
-
0.0
147*
MXU2.1
03:32:46.34
27:46:32.1
25.14
5.09
0.65
-
0.0
148
15
03:32:35.22
27:53:17.9
-
-
0.00
-
0.0
149
03:32:12.30
27:46:21.8
23.05
4.60
42.8
0.10
1.033
LEX
AGN-2
1.0
ref
1:
[O
II]
150
78
03:32:25.16
27:54:50.1
23.02
5.31
43.2
1.00
1.090
ABS
AGN-2
2.0+
4200 A-
151
6+7
03:32:20.48
27:47:32.3
22.52
4.54
42.8
1.00
0.604
LEX
AGN-2
2.0+
151
22+23+24
03:32:20.48
27:47:32.3
22.52
4.54
42.8
1.00
0.604
LEX
AGN-2
1.0
3900 A-
152
36+39+40
03:32:59.31
27:48:58.9
23.04
4.66
0.53
-
0.0
Not
centered
152
MXU2.1
03:32:59.33
27:48:59.0
23.04
4.66
0.53
-
0.0
153
6+7
03:32:18.35
27:50:55.3
24.20
5.68
43.9
0.59
1.536
HEX
AGN-2
2.0+
HeII?,
CIV
155
24
03:32:07.98
27:42:39.4
22.37
3.55
42.2
0.16
0.545
LEX
AGN-2
2.0+
line
ratios
156
MXU4.1
03:32:13.23
27:55:28.7
22.81
5.12
43.5
1.00
1.185
ABS
AGN-2
2.0+
[NEV]?
170
15
03:32:46.41
27:54:14.0
20.69
4.46
42.3
0.17
0.664
ABS
AGN-2
2.0+
[OII]?
171
84
03:32:35.10
27:44:10.9
23.55
4.12
0.01
-
0.0
171
03:32:35.19
27:44:11.6
23.55
4.12
42.5
0.01
0.839
LEX
AGN-2
1.0
ref
1:
[O
II]
173
MXU5.1
03:32:16.74
27:43:27.7
22.31
3.57
40.9
1.00
0.524
LEX
gal
2.0+
[OII]?
173
MXU1.1
03:32:16.76
27:43:27.5
22.31
3.57
40.9
1.00
0.524
LEX
gal
2.0+
175a
36
03:32:52.06
27:44:35.1
20.10
2.67
40.5
1.00
0.277
LEX
gal
2.0
line
ratios
175b
39+40
03:32:51.86
27:44:36.7
20.27
3.27
41.1
1.00
0.522
HEX
gal
2.0+
possible
low
LX
AGN-2,
[NeV]
176
36+39+40
03:33:09.25
27:44:50.0
22.25
NA
43.0
0.27
0.786
LEX
AGN-1
2.0+
6600 A-
177a
137
03:32:56.98
27:50:08.8
23.78
5.42
1.00
-
0.0
177b
137
03:32:56.86
27:50:08.5
25.69
<5.39
1.00
-
0.0
178
6+7
03:32:13.87
27:50:34.0
26.02
<5.72
1.00
-
0.0
184
15
03:32:48.18
27:52:56.8
20.97
4.35
42.5
0.39
0.667
ABS
AGN-2
2.0+
185
22+23+24
03:32:10.92
27:43:43.3
21.80
4.01
0.13
-
0.0
185
MXU1.1
03:32:10.94
27:43:43.1
21.80
4.01
0.13
-
0.0

{ 74 {
Table
5|Continued
No
mask

ô
R
R
K
LX
HR
z
Class
Class
Qual
Comments
(J2000)
(J2000)
(mag)
(mag)
log
erg s


(opt)
(X-ray)
185
134
03:32:10.92
27:43:43.3
21.80
4.01
0.13
-
0.0
5000 A-
185
MXU5.1
03:32:10.92
27:43:43.3
21.80
4.01
0.13
-
0.0
186
40
03:32:52.34
27:45:56.4
23.09
2.72
1.00
-
0.0
186
86
03:32:52.34
27:45:56.7
23.09
2.72
1.00
-
0.0
186
146
03:32:52.34
27:45:56.7
23.09
2.72
1.00
-
0.0
186
MXU2.1
03:32:52.34
27:45:56.7
23.09
2.72
1.00
-
0.0
188
122
03:32:22.56
27:49:49.8
22.88
4.73
42.2
1.00
0.734
LEX
AGN-2
2.0+
189d
146
03:32:45.73
27:42:12.9
23.19
5.29
42.6
1.00
0.755
LEX
AGN-2
2.0+
190
28+29
03:32:35.86
27:40:59.6
22.39
4.35
42.9
1.00
0.733
LEX
AGN-2
2.0+
line
ratios
190
46+47
03:32:35.86
27:40:59.6
22.39
4.35
42.9
1.00
0.735
LEX
AGN-2
2.0+
200a
46+47
03:32:54.97
27:45:07.1
23.53
4.96
0.14
-
0.0
5400 A-
200b
46+47
03:32:54.72
27:45:05.9
24.54
<4.24
0.14
-
0.0
201b
84
03:32:38.94
27:44:39.4
24.34
<4.04
42.7
0.06
0.679
HEX
AGN-2
2.0+
H
,
[NeV],
line
ratios
202
78
03:32:29.86
27:51:05.8
23.97
3.37
44.6
0.11
3.700
HEX
QSO-2
2.0+
C
IV,
HeII,
NV,
OVI
204
22+23+24
03:32:23.15
27:45:54.9
23.42
4.43
1.00
-
0.0
4600 A-
204
MXU1.1
03:32:23.20
27:45:54.7
23.42
4.43
1.00
-
0.0
204
03:32:23.23
27:45:55.3
23.42
4.43
41.9
1.00
1.223
LEX
gal
2.0+
ref
1,
[O
II]
205b
82
03:32:17.48
27:41:36.1
24.23
<3.93
0.16
-
0.0
205c
82
03:32:17.55
27:41:35.4
24.90
<4.60
42.3
0.16
0.53
LEX
AGN-2
0.5
206
MXU5.1
03:32:16.20
27:39:30.6
19.81
2.29
44.5
0.54
1.324
BLAGN
QSO-1
2.0+
Mg
II
207a
MXU5.1
03:32:07.90
27:37:33.7
24.03
NA
0.36
-
0.0
209
MXU11.1
03:31:47.22
27:53:14.3
24.63
4.71
0.33
-
0.0
211
122
03:32:05.91
27:54:49.7
21.10
4.33
41.8
1.00
0.679
ABS
gal
2.0+
-7900 A
217b
15
03:32:33.30
27:52:03.6
25.77
<5.47
1.00
-
0.0
218a
6+7
03:32:16.38
27:52:01.3
23.38
3.14
41.9
0.37
0.497
LEX
gal
0.5
218b
78
03:32:16.41
27:51:59.2
25.78
<5.48
0.37
-
0.0
218b
119+120+121
03:32:16.42
27:51:59.2
25.78
<5.48
0.37
-
0.0
220a
119+120+121
03:32:32.75
27:51:51.3
23.30
5.20
1.00
-
0.0
contamination
220b
6+7
03:32:32.48
27:51:49.5
22.91
<2.61
1.00
-
0.0
5600 A-
221
82
03:32:08.86
27:44:24.7
-
-
1.00
-
0.0
221
MXU1.1
03:32:08.86
27:44:24.7
-
-
1.00
-
0.0
222
46+47
03:32:54.52
27:45:02.0
23.81
5.26
0.40
-
0.0
5350 A-
222
146
03:32:54.52
27:45:02.0
23.81
5.26
0.40
-
0.0
6500 A-
224
23+24
03:32:28.73
27:46:20.4
22.03
4.22
41.8
1.00
0.738
ABS
gal
2.0+
6600 A-

{ 75 {
Table
5|Continued
No
mask

ô
R
R
K
LX
HR
z
Class
Class
Qual
Comments
(J2000)
(J2000)
(mag)
(mag)
log
erg s


(opt)
(X-ray)
224
84
03:32:28.73
27:46:20.4
22.03
4.22
41.8
1.00
0.738
LEX
gal
2.0+
5600 A-
229
36
03:32:56.31
27:48:33.8
17.06
2.68
39.8
1.00
0.103
ABS
gal
2.0+
contamination
229
MXU2.1
03:32:56.33
27:48:34.0
17.06
2.68
39.8
1.00
0.105
ABS
gal
2.0+
230
MXU11.1
03:31:53.55
27:48:43.1
24.21
<3.91
43.6
0.45
2.174
BLAGN
AGN-1
2.0+
C
IV
230
MOS11.1
03:31:53.55
27:48:43.1
24.21
<3.91
43.6
0.45
2.185
BLAGN
AGN-1
2.0+
C
IV
233
7
03:32:25.76
27:49:36.3
20.46
3.83
41.0
1.00
0.577
LEX
gal
2.0+
5150 A-,
contamination
236
6+7
03:32:11.47
27:50:06.9
23.85
5.20
0.47
-
0.0
236
MXU4.1
03:32:11.46
27:50:06.8
23.85
5.20
0.47
-
0.0
237
137
03:32:58.53
27:50:07.8
17.80
4.07
1.00
0
M-star
M-star
2.0+
-8950 A.
M-5
or
6
238
MXU11.1
03:31:47.97
27:50:45.5
23.53
3.14
43.6
0.46
1.065
BLAGN
AGN-1
2.0+
Mg
II,
[NeV]
239a
15
03:32:36.18
27:51:26.6
24.57
4.29
0.27
-
0.0
239a
119+120+121
03:32:36.18
27:51:26.6
24.57
4.29
0.27
-
0.0
4500 A-
239b
119+120+121
03:32:36.31
27:51:28.5
25.53
<5.23
0.27
-
0.0
4500 A-
241
82
03:32:24.21
27:42:57.7
24.76
4.73
0.36
-
0.0
4550 A-
241
84
03:32:24.21
27:42:57.7
24.76
4.73
0.36
-
0.0
242
46+47
03:32:51.84
27:42:29.6
22.49
4.43
42.4
1.00
1.027
LEX
AGN-1
2.0+
243
MXU5.1
03:32:08.40
27:40:46.9
-
-
0.04
-
0.0
247
03:32:35.10
27:55:33.2
16.27
3.31
39.7
0.31
0.038
LEX
gal
2.0+
ULX,
2dF
TGS243Z011
248
MXU4.1
03:32:10.20
27:54:16.2
23.18
4.65
42.3
0.15
0.685
ABS
AGN-2
2.0+
251a
6+7
03:32:07.26
27:52:31.3
23.85
<3.55
0.04
-
0.0
-8100 A
251a
MOS11.1
03:32:07.18
27:52:31.7
23.85
<3.55
0.04
-
0.0
4500 A-
251b
MXU4.1
03:32:07.27
27:52:29.1
24.49
4.97
0.04
-
0.0
251b
MOS11.1
03:32:07.17
27:52:29.5
24.49
4.97
0.04
-
0.0
4500 A-
252
39+40
03:32:47.05
27:43:46.4
23.25
4.57
43.2
0.52
1.172
LEX
AGN-2
2.0+
252
46+47
03:32:47.03
27:43:46.8
23.25
4.57
43.2
0.52
1.180
LEX
AGN-2
2.0+
4750 A-
252
146
03:32:47.03
27:43:46.8
23.25
4.57
43.2
0.52
1.178
LEX
AGN-2
2.0+
253
22+23+24
03:32:20.05
27:44:47.4
24.94
4.95
42.4
0.66
0.484
LEX
AGN-2
1.0
3500 A-
253
MXU1.1
03:32:20.08
27:44:47.2
24.94
4.95
42.4
0.66
0.481
LEX
AGN-2
1.0
254
138+139
03:32:19.89
27:45:18.0
23.87
<3.57
1.00
-
0.0
254
MXU1.1
03:32:19.92
27:45:17.8
23.87
<3.57
1.00
-
0.0
256
39+40
03:32:43.03
27:48:44.2
24.36
4.01
0.57
-
0.0
-8200 A
256
86
03:32:43.05
27:48:44.7
24.36
4.01
0.57
-
0.0
256
MXU2.1
03:32:43.05
27:48:44.7
24.36
4.01
0.57
-
0.0
257a
6+7
03:32:13.38
27:48:57.7
24.17
<3.87
0.35
-
0.0

{ 76 {
Table
5|Continued
No
mask

ô
R
R
K
LX
HR
z
Class
Class
Qual
Comments
(J2000)
(J2000)
(mag)
(mag)
log
erg s


(opt)
(X-ray)
257b
6+7
03:32:13.19
27:48:56.0
22.57
2.82
42.2
0.35
0.549
LEX
AGN-2
1.0
259
78
03:32:06.12
27:49:27.8
24.44
5.19
0.58
-
0.0
259
122
03:32:06.12
27:49:27.8
24.44
5.19
0.58
-
0.0
-8000 A
259
MXU4.1
03:32:06.12
27:49:27.8
24.44
5.19
0.58
-
0.0
259
MOS11.1
03:32:06.04
27:49:28.3
24.44
5.19
0.58
-
0.0
260
15
03:32:25.11
27:50:43.3
23.81
3.85
42.7
0.23
1.043
LEX
AGN-2
2.0+
261
MXU11.1
03:31:57.11
27:51:19.4
-
-
0.50
-
0.0
263a
78
03:32:18.87
27:51:34.3
24.68
<4.38
42.5
0.31
0.70
LEX
AGN-2
0.5
263b
MXU4.1
03:32:18.83
27:51:35.6
25.33
5.06
44.2
0.31
3.660
HEX
QSO-2
2.0+
CIV
264
6+7
03:32:29.76
27:51:47.1
23.44
<3.14
43.2
0.60
1.318
LEX
AGN-2
1.0
5000 A-
264
15
03:32:29.76
27:51:47.1
23.44
<3.14
43.2
0.60
1.315
LEX
AGN-2
1.0
264
122
03:32:29.76
27:51:47.1
23.44
<3.14
43.2
0.60
1.316
LEX
AGN-2
1.0
5350-
266
82
03:32:13.86
27:42:49.0
21.70
3.91
42.5
1.00
0.735
LEX
AGN-2
2.0+
267
82
03:32:04.84
27:41:27.7
23.72
3.70
1.00
-
0.0
267
MXU5.1
03:32:04.87
27:41:27.6
23.72
3.70
43.0
1.00
0.720
LEX
AGN-2
1.0
MgII
268a
46
03:32:49.20
27:40:50.6
22.33
4.55
43.6
1.00
1.222
HEX
AGN-2
2.0+
He
II,
[NeIV]
511a*
146
03:32:36.50
27:46:29.2
22.29
3.57
42.2
0.24
0.767
LEX
AGN-1/grp
2.0
6450 A-
511a*
MXU2.1
03:32:36.50
27:46:29.2
22.29
3.57
42.2
0.24
0.764
LEX
AGN-1
2.0
511b*
146
03:32:36.47
27:46:28.3
23.26
<2.96
0.24
-
0.0
6450 A-
512
134
03:32:34.50
27:43:50.3
22.07
4.10
42.3
0.14
0.665
LEX
AGN-2
2.0+
512
146
03:32:34.35
27:43:50.3
22.07
4.10
42.3
0.14
0.668
LEX
AGN-2
2.0+
513a
119+120+121
03:32:34.02
27:49:00.9
26.06
<5.76
0.23
-
0.0
513b
MXU2.1
03:32:34.10
27:48:58.3
26.25
<5.95
0.23
-
0.0
514*
03:32:33.47
27:43:13.1
17.03
2.80
40.4
0.14
0.103
ABS
gal
2.0+
ULX,
2dF
TGS243Z010
515
MXU2.1
03:32:32.16
27:46:51.6
-
-
0.41
-
0.0
516
134
03:32:31.36
27:47:24.9
21.40
3.00
42.2
0.26
0.667
LEX
AGN-1
2.0+
5050A-
516
MXU1.1
03:32:31.40
27:47:24.7
21.40
3.00
42.2
0.26
0.665
LEX
AGN-1
2.0+
518
MXU1.1
03:32:26.76
27:46:04.1
-
-
0.01
-
0.0
519
122
03:32:25.87
27:55:06.4
23.38
3.47
42.8
0.03
1.034
LEX
AGN-2
2.0+
4100 A-
521
119+120+121
03:32:22.76
27:52:24.0
20.10
2.45
40.5
0.40
0.131
LEX
gal
2.0+
line
ratios
522a*
122
03:32:21.41
27:55:49.8
24.13
<3.83
0.34
-
0.0
522b*
122
03:32:21.40
27:55:48.7
24.81
<4.51
0.34
-
0.0
523
MXU5.1
03:32:20.35
27:42:28.1
-
-
0.08
-
0.0
524
138+139
03:32:19.96
27:42:43.3
-
-
0.04
-
0.0

{ 77 {
Table
5|Continued
No
mask

ô
R
R
K
LX
HR
z
Class
Class
Qual
Comments
(J2000)
(J2000)
(mag)
(mag)
log
erg s


(opt)
(X-ray)
524
MXU5.1
03:32:20.02
27:42:43.8
-
-
0.04
-
0.0
525
138
03:32:19.80
27:41:22.8
19.15
3.11
41.4
0.01
0.229
LEX
AGN-2
2.0+
line
ratios:
low
LX
AGN-2
526a
134
03:32:18.70
27:44:13.0
23.55
4.93
0.18
-
0.0
526a
138+139
03:32:18.70
27:44:13.0
23.55
4.93
0.18
-
0.0
526a
MXU1.1
03:32:18.73
27:44:12.7
23.55
4.93
0.18
-
0.0
526b
138+139
03:32:18.63
27:44:11.7
24.71
<4.41
0.18
-
0.0
526b
MXU1.1
03:32:18.66
27:44:11.6
24.71
<4.41
0.18
-
0.0
526c
03:32:18.82
27:44:13.0
22.99
NA
42.5
0.18
0.958
LEX
AGN-2
2.0
ref
1,
[O
II]
527*
MXU4.1
03:32:18.54
27:54:13.1
-
-
0.29
-
0.0
528
MXU4.1
03:32:17.15
27:54:02.4
23.41
<3.11
0.10
-
0.0
530
MXU5.1
03:32:14.90
27:38:43.9
23.23
NA
0.33
-
0.0
531
119+120+121
03:32:14.44
27:51:10.9
23.73
4.69
43.3
0.41
1.544
HEX
AGN-2
2.0+
HeII,
CIV
531
MXU4.1
03:32:14.44
27:51:10.9
23.73
4.69
43.3
0.41
1.544
HEX
AGN-2
2.0+
He
II,
C
IV
534
134
03:32:12.21
27:45:30.2
21.67
4.06
42.2
0.34
0.676
LEX
AGN-2
2.0+
[NeV]?
535
138+139
03:32:11.42
27:46:50.0
22.01
3.81
42.3
0.01
0.575
LEX
AGN-2
2.0+
538
138
03:32:08.55
27:46:48.4
19.18
3.96
41.4
0.08
0.310
LEX
AGN-2
2.0+
-8750 A,
line
ratios,
low
LX
AGN-2
539
MXU5.1
03:32:04.05
27:37:25.5
23.95
NA
43.7
0.40
0.977
BLAGN
AGN-1
2.0+
Mg
II,
[O
II]
540
MXU4.1
03:32:02.57
27:50:52.6
25.37
4.83
0.05
-
0.0
541
MXU11.1
03:31:59.75
27:49:49.5
-
K20.33
0.08
-
0.0
542
MOS11.1
03:31:58.44
27:54:37.2
-
-
0.16
-
0.0
543a
MOS11.1
03:31:56.90
27:51:02.0
26.06
<5.76
0.17
-
0.0
547a
MXU11.1
03:31:50.40
27:52:38.0
24.45
<4.15
43.8
0.24
2.316
LEX
AGN-2
1.0
549
03:32:22.61
27:58:04.1
11.44W
2.05TM
1.00
0
star
star
2.0+
TYC
6453-888-1
552
121
03:32:15.80
27:53:24.7
22.62
4.33
41.6
1.00
0.673
LEX
gal
2.0+
-7800 A
552
122
03:32:15.80
27:53:24.7
22.62
4.33
41.6
1.00
0.674
LEX
gal
2.0+
553a
137
03:32:56.66
27:53:16.6
20.02
2.28
41.0
1.00
0.366
LEX
gal
2.0+
5900 A-,
line
ratios
554
MXU11.1
03:31:50.77
27:53:01.1
24.32
<4.02
1.00
-
0.0
560*
138+139
03:32:06.29
27:45:36.8
21.93
4.21
41.4
1.00
0.669
ABS
gal/grp
2.0+
-8550 A,
[OII]?
561a
MXU1.1
03:32:22.45
27:45:44.3
-
-
1.00
-
0.0
563
134
03:32:31.47
27:46:23.2
23.30
4.49
1.00
-
0.0
3800 A-
563
MXU2.1
03:32:31.47
27:46:23.2
23.30
4.49
1.00
-
0.0
563
03:32:31.54
27:46:24.6
23.30
4.49
42.4
1.00
2.223
HEX
AGN-1
2.0+
ref
4:
narrow
HeII,
CIII]
565
119+120+121
03:32:24.85
27:47:06.4
20.69
3.07
40.4
1.00
0.368
LEX
gal
2.0+
5950 A-,
line
ratios
565
134
03:32:24.85
27:47:06.4
20.69
3.07
40.4
1.00
0.363
LEX
gal
2.0+

{ 78 {
Table
5|Continued
No
mask

ô
R
R
K
LX
HR
z
Class
Class
Qual
Comments
(J2000)
(J2000)
(mag)
(mag)
log
erg s


(opt)
(X-ray)
567a
134
03:32:38.78
27:47:32.2
21.12
2.96
40.8
1.00
0.460
LEX
gal
2.0+
6000 A-,
line
ratios
567a
137
03:32:38.78
27:47:32.2
21.12
2.96
40.8
1.00
0.456
LEX
gal
2.0+
567b
137
03:32:38.88
27:47:33.3
23.19
<2.89
1.00
-
0.0
570
138+139
03:32:22.54
27:48:04.3
24.58
<4.28
1.00
-
0.0
572
MXU1.1
03:32:22.25
27:48:11.0
26.95
<6.65
1.00
-
0.0
573
137
03:32:44.44
27:48:19.0
20.58
3.33
40.6
1.00
0.414
LEX
gal
2.0+
-8000 A
575
119+120+121
03:32:17.08
27:49:21.7
19.70
3.48
40.5
1.00
0.340
ABS
gal
2.0+
[OII]?
577a
89
03:32:36.18
27:49:31.8
20.99
4.09
1.00
-
0.0
577a
119+120
03:32:36.18
27:49:31.8
20.99
4.09
41.3
1.00
0.547
LEX
gal
2.0+
6350A-
579a
119+120+121
03:32:34.16
27:49:39.5
25.29
<4.99
1.00
-
0.0
579a
137
03:32:34.15
27:49:39.5
25.29
<4.99
1.00
-
0.0
579b
119+120+121
03:32:34.05
27:49:37.8
24.93
5.50
1.00
-
0.0
5700 A-
579b
137
03:32:34.05
27:49:37.8
24.93
5.50
1.00
-
0.0
580a
119+120
03:32:16.17
27:49:41.9
21.22
4.32
41.1
1.00
0.664
HEX
gal
2.0+
interacting,
[NeV],
possible
low
LX
AGN-1
580b
121
03:32:15.98
27:49:43.3
21.69
4.60
41.1
1.00
0.666
ABS
gal
2.0
interacting
581*
MXU4.1
03:32:07.36
27:49:41.9
24.38
<4.08
1.00
-
0.0
581*
MOS11.1
03:32:07.27
27:49:42.6
24.38
<4.08
1.00
-
0.0
4100 A-
582b
89
03:32:38.83
27:49:56.3
20.21
NA
40.2
1.00
0.242
LEX
gal
2.0+
line
ratios
582b
137
03:32:38.83
27:49:56.3
20.21
NA
40.2
1.00
0.241
LEX
gal
2.0+
583
MXU4.1
03:32:13.92
27:50:01.2
-
K19.81
1.00
-
0.0
584
119
03:32:17.86
27:50:07.1
20.32
3.50
1.00
0
M-star
M-star
2.0+
around
M-5
585a
MXU11.1
03:31:55.12
27:50:28.6
23.77
5.88
42.0
1.00
1.212
LEX
AGN-1
1.0
586
137
03:32:39.47
27:50:31.9
22.23
4.23
41.1
1.00
0.580
ABS
gal
2.0+
587
121
03:32:15.28
27:50:39.4
21.00
2.89
40.1
1.00
0.245
ABS
gal
2.0+
587
122
03:32:15.28
27:50:39.4
21.00
2.89
40.1
1.00
0.246
ABS
gal
2.0+
588
MXU11.1
03:31:55.61
27:50:43.9
19.80
3.99
1.00
0
M-star
M-star
2.0+
590a
122
03:32:07.12
27:51:29.1
25.07
<4.77
1.00
-
BLLAC?
0.0
BLLAC?,
-8400 A
591
MOS11.1
03:31:44.88
27:51:38.9
-
-
1.00
-
0.0
-7500 A
593
138+139
03:32:14.70
27:44:02.9
25.87
<5.57
1.00
-
0.0
593
MXU1.1
03:32:14.81
27:44:02.6
25.87
<5.57
1.00
-
0.0
595
MXU5.1
03:32:15.77
27:39:54.2
25.71
<5.41
1.00
-
0.0
4000 A-
598
MXU4.1
03:32:24.68
27:54:11.6
21.18
3.17
41.9
1.00
0.617
ABS
AGN-2
2.0+
599
122
03:32:29.81
27:53:30.1
25.16
<4.86
1.00
-
0.0
600
MXU1.1
03:32:13.86
27:45:25.7
23.77
5.22
1.00
-
0.0

{ 79 {
Table
5|Continued
No
mask

ô
R
R
K
LX
HR
z
Class
Class
Qual
Comments
(J2000)
(J2000)
(mag)
(mag)
log
erg s


(opt)
(X-ray)
600
03:32:13.88
27:45:26.5
23.77
5.22
42.9
1.00
1.327
LEX
AGN-2
2.0+
ref
1
601
134
03:32:18.45
27:45:56.0
22.05
4.58
42.2
1.00
0.735
ABS
AGN-2
2.0+
602
134
03:32:21.98
27:46:55.8
21.55
4.48
42.2
1.00
0.668
ABS
AGN-2
2.0+
603
MXU2.1
03:32:57.68
27:47:10.8
25.52
4.82
1.00
-
0.0
606a
122
03:32:24.97
27:50:08.0
25.26
4.30
42.9
1.00
1.037
LEX
AGN-2
1.0
3800 A-
609
119+120+121
03:32:36.20
27:50:37.1
24.98
5.52
1.00
-
0.0
5300 A-
609
137
03:32:36.20
27:50:37.1
24.98
5.52
1.00
-
0.0
610
MXU4.1
03:32:19.85
27:51:58.6
-
-
1.00
-
0.0
611a
146
03:32:41.72
27:43:28.5
23.29
4.65
42.7
1.00
0.979
LEX
AGN-2
1.0
611b
146
03:32:41.55
27:43:27.9
23.67
4.97
1.00
-
0.0
612a
138+139
03:32:21.34
27:42:28.8
22.57
3.18
41.9
1.00
0.387
LEX
AGN-2
2.0
4200 A-
612b
138+139
03:32:21.43
27:42:31.2
21.88
3.94
42.6
1.00
0.736
LEX
AGN-2
2.0+
4200 A-
615
MXU4.1
03:32:01.29
27:50:50.8
23.41
4.47
42.3
0.08
0.759
LEX
AGN-2
2.0+
615
MOS11.1
03:32:01.21
27:50:51.4
23.41
4.47
42.3
0.08
0.759
LEX
AGN-2
2.0+
619
MOS11.1
03:31:55.62
27:54:02.4
22.73
2.95
1.00
-
0.0
620a
119+120+121
03:32:30.15
27:53:05.9
21.43
2.71
41.2
1.00
0.648
LEX
gal
2.0+
621
122
03:32:16.57
27:52:45.5
24.70
<4.40
1.00
-
0.0
621
MXU4.1
03:32:16.57
27:52:45.5
24.70
<4.40
1.00
-
0.0
623a
MXU1.1
03:32:28.46
27:47:00.0
24.86
4.40
1.00
-
0.0
624
134
03:32:29.21
27:47:07.6
21.70
4.39
41.2
1.00
0.669
ABS
gal
2.0+
4400 A-
624
138+139
03:32:29.21
27:47:07.6
21.70
4.39
41.2
1.00
0.668
ABS
gal
2.0+
4600 A-
626
138+139
03:32:09.48
27:47:57.1
25.35
<5.05
1.00
-
0.0
-8600 A
627
120
03:32:23.35
27:48:52.5
19.84
2.11
40.1
1.00
0.248
LEX
gal
2.0+
3750 A-,
line
ratios
630
146
03:32:28.28
27:44:03.7
23.05
5.32
1.00
-
0.0
6000 A-
631
138+139
03:32:15.08
27:43:35.5
24.35
5.59!
1.00
-
0.0
633
MXU11.1
03:31:50.43
27:52:12.2
24.01
4.69
43.2
1.00
1.374
HEX
AGN-2
2.0+
HeII,
Mg
II,
[NeV]
634
MXU2.1
03:32:51.42
27:47:46.9
24.86
4.87
1.00
-
0.0
635a
MXU4.1
03:32:16.78
27:50:07.9
23.01
4.51
42.1
1.00
0.729
ABS
AGN-2
2.0
more
counterparts?
638
146
03:32:29.95
27:43:01.3
23.67
4.37
1.00
-
0.0
640
MXU5.1
03:32:17.66
27:38:51.4
-
NA
1.00
-
0.0
642
138+139
03:32:15.19
27:41:58.9
24.54
4.01
43.7
0.25
2.402
HEX
AGN-2
2.0+
CIV
643
MOS11.1
03:31:56.32
27:52:56.5
24.96
<4.66
0.08
-
0.0
646
134
03:32:45.10
27:47:24.1
21.01
3.62
40.8
1.00
0.438
LEX
gal
2.0+
6500 A-
647
03:33:01.82
27:50:09.4
17.50
2.44
1.00
0
star
star
2.0+
ref
3

{ 80 {
Table
5|Continued
No
mask

ô
R
R
K
LX
HR
z
Class
Class
Qual
Comments
(J2000)
(J2000)
(mag)
(mag)
log
erg s


(opt)
(X-ray)
652
146
03:32:49.33
27:43:02.3
20.64
1.89
39.3
1.00
0.077
LEX
gal
2.0+
5800 A-,
line
ratios
901
MXU2.1
03:32:35.72
27:49:16.0
25.16
5.10
42.5
1.00
2.578
HEX
AGN-1
2.0+
CIV,
NV
Cluster
members
for
extended
source
249
(with
associated
point
source)
249a
122
03:32:19.29
27:54:06.0
21.72
5.25
42.6
0.12
0.964
ABS
AGN-2
2.0+
interacting,
within
X-ray
error
circle
249b
122
03:32:19.29
27:54:03.3
23.15
4.96
42.6
0.12
0.964
LEX
gal
2.0
interacting
249c
MXU4.1
03:32:17.25
27:54:04.9
23.50
<3.20
42.6
0.12
0.962
LEX
gal
1.0
Cluster
members
for
extended
source
566
(with
associated
point
source)
566a
6+7
03:32:18.02
27:47:18.5
20.62
4.88
41.8
1.00
0.734
LEX
gal
2.0+
566a
134
03:32:18.02
27:47:18.5
20.62
4.88
41.8
1.00
0.734
LEX
gal
2.0+
566b
22+23+24
03:32:20.65
27:47:17.1
21.78
3.52
41.8
1.00
0.733
LEX
1.0
not
centered,
contaminated,
3900 A-
Cluster
members
for
extended
source
594
(with
associated
point
source)
594a
22
03:32:09.71
27:42:48.2
21.52
4.53
41.9
1.00
0.733
LEX
gal
2.0+
594a
138
03:32:09.71
27:42:48.2
21.52
4.53
41.9
1.00
0.733
LEX
gal
2.0+
594c
82
03:32:09.20
27:42:25.7
22.92
4.60
41.9
1.00
0.734
ABS
gal
2.0+
594c
MXU5.1
03:32:09.20
27:42:25.7
22.92
4.60
41.9
1.00
0.734
ABS
gal
2.0+
594d
MXU5.1
03:32:08.54
27:42:17.8
22.09
4.61
41.9
1.00
0.732
ABS
gal
2.0+
594e
99
03:32:09.40
27:42:36.4
23.10
4.52
41.9
1.00
-
gal
0.0
594e
138
03:32:09.40
27:42:36.2
23.10
4.52
41.9
1.00
0.731
ABS
gal
2.0
G-band
Cluster
members
for
extended
source
645
(no
associated
point
source)
645a
MXU11.1
03:31:49.79
27:49:40.0
21.61
4.87
42.0
1.00
0.679
ABS
gal
2.0+
645b
MXU11.1
03:31:51.66
27:49:30.7
21.51
4.51
42.0
1.00
0.683
ABS
gal
2.0
Note.
|
ref
1:
A.
Cimatti
&
R.
Gilli,
private
communication,
ref
2:
paper
I:
Giacconi
et
al.
2001,
ApJ
551,624,
ref
3:
C.
Wolf,
private
communication,
ref
4:
Daddi
et
al.
(2003)
See
Section
7
for
explanation
of
columns.

{ 81 {
*:
extended
X-ray
source.
See
Table
6
for
diagnostics
on
line
ratios.

{ 82 {
Table 6. Line ratios.
No log [OIII]
H log [SII]
H log [NII]
H log [OI]
H Class
[5007  A/4861  A] [6716+6731  A/6563  A] [6583  A/6563  A] [6300  A/6563  A]
41 0.98 - - - Seyfert II
75 0.56 - - - -
155 0.94 - - - Seyfert II
175a 0.25 0.58 0.60 - NELG
190 1.00 - - - Seyfert II
201b 0.88 - - - Seyfert II
521 0.26 - x 0.98 LINER
525 >1.0 - 0.04 x - Seyfert II
538 0.73 - 0.03 - Seyfert II
553a 0.56 0.94 - - HII region
565 0.07 0.51 0.46 - NELG
567a 0.11 - - - -
582b <0.0 - 0.39 - -
627 0.28 0.61 - - NELG
652 - 0.48 - - -
Note. | Traditional line ratios used for classication of emission-line galaxies. We only measured line
strengths for objects with suôtiently high signal-to-noise spectra.
The classication as Seyfert II, LINER, NELG or HII region is derived from the line ratio diagnostics
given by Ho et al. (1993).
x possible broad H component.

{ 83 {
Table 7. Optical spectroscopy results for eld galaxies.
No mask  ô R z Class Qual Comments
(J2000) (J2000) (mag)
00012 MXU11.1 03:31:59.60 27:50:10.7 20.17 0 star 2
00338 82 03:32:01.00 27:46:15.5 22.52 0.334 NELG 2 4200  A-
02008 99 03:32:05.80 27:41:45.2 20.71 0 M-star 2
02045 78 03:32:05.97 27:48:45.8 21.69 0.196 NELG 2
02124 138+139 03:32:06.26 27:45:42.7 17.37 0.000 star 2
02215 MXU4.1 03:32:06.59 27:50:38.2 20.55 0.339 NELG 2
02215 MXU11.1 03:32:06.49 27:50:38.7 20.55 0.337 NELG 2 4900  A-, contaminated
02311 99 03:32:06.88 27:42:07.7 21.08 0.286 gal 2
02311 MXU5.1 03:32:06.89 27:42:07.7 21.08 0.283 NELG 2
02569 88 03:32:07.58 27:48:40.6 18.58 0 star? -8450  A, star?
02593 6+7 03:32:07.67 27:47:31.5 19.29 0 M-star 2 M5+ star
02869 MXU5.1 03:32:08.44 27:42:43.5 21.83 0.420 NELG 2
02910 88 03:32:08.55 27:46:48.4 19.18 0.310 NELG 2 -8800  A
02969 78 03:32:08.69 27:52:11.5 24.67 0.561 NELG 1
03204 138 03:32:09.40 27:42:36.2 23.10 0.731 gal 2
03268 138+139 03:32:09.58 27:42:41.9 23.77 0.681 NELG 2
03470 88 03:32:10.08 27:49:07.3 18.86 0 Star 2
04024 138+139 03:32:11.60 27:46:59.2 22.72 0.816 NELG 2
04356 MXU5.1 03:32:12.47 27:39:32.8 20.60 0.214 NELG 2
04500 122 03:32:12.90 27:52:27.9 24.22 0.741 NELG 1
04766 6+7 03:32:13.69 27:49:15.2 22.98 0.538 NELG 2
04888 22+23+24 03:32:14.03 27:46:34.3 23.76 0.836 NELG 1
05395 121 03:32:15.38 27:50:45.1 19.00 0.23 gal 1 Halo only
05614 MXU4.1 03:32:15.99 27:53:50.1 17.92 0 star 2
05619 MXU4.1 03:32:16.00 27:52:11.9 19.39 0 M-star 2 Early
05857 MXU5.1 03:32:16.70 27:43:24.4 21.66 0 M-star 2
06215 6+7 03:32:17.58 27:49:41.1 22.01 0.337 NELG 2
06312 88 03:32:17.84 27:46:28.0 18.10 0 Star 2
06629 138+139 03:32:18.73 27:44:16.1 21.62 0.603 gal 1
06683 88 03:32:18.84 27:45:29.4 19.16 0.450 gal 1 Sky residuals
06780 138+139 03:32:19.14 27:47:59.5 21.31 0.228 NELG 2
06861 MXU4.1 03:32:19.36 27:53:31.0 18.71 0 star 2 Late-K or early M
06894 MXU5.1 03:32:19.48 27:42:16.8 20.81 0.382 gal 2
06913 78 03:32:19.52 27:54:43.2 23.69 0.247 NELG 1 5100  A-
07159 78 03:32:20.27 27:52:22.1 20.36 0.343 NELG 2
07210 122 03:32:20.44 27:49:14.2 22.63 0.115 NELG 2
07511 78 03:32:21.23 27:52:23.6 25.52 0.863 NELG 1
07694 MXU4.1 03:32:21.77 27:54:09.8 19.93 0 star 2
07894 119+120+121 03:32:22.33 27:45:59.9 22.76 0.727 NELG 1 6400  A-, edge
07993 134 03:32:22.59 27:44:26.0 21.07 0.738 NELG 2
07993 138+139 03:32:22.59 27:44:26.0 21.07 0.737 NELG 2 3800  A-, partly on slit
08145 122 03:32:22.97 27:55:29.4 24.05 0.780 NELG 1
08198 134 03:32:23.16 27:44:23.0 22.69 0.739 NELG 1
08302 84 03:32:23.47 27:42:57.9 24.89 1.020 NELG 1
08351 MXU1.1 03:32:23.67 27:46:56.6 18.05 0 Star 2

{ 84 {
Table 7|Continued
No mask  ô R z Class Qual Comments
(J2000) (J2000) (mag)
08619 78 03:32:24.53 27:54:43.0 19.24 0.126 NELG 1 4200  A-
09290 46+47 03:32:26.53 27:43:03.8 21.04 0.216 NELG 1 6900  A-
09479 78 03:32:27.06 27:54:16.3 24.14 1.405 BLAGN 1 3600  A-
09511 84 03:32:27.15 27:41:45.9 20.66 0 Star 2
09949 146 03:32:28.15 27:43:08.1 23.33 0.339 NELG 2 5100  A-
10024 MXU1.1 03:32:28.37 27:48:07.3 19.93 0 M-star 2
10444 138+139 03:32:28.96 27:46:55.9 22.00 0.301 gal 2 4600  A-
11210 122 03:32:29.83 27:53:41.0 23.77 0.987 NELG 1 5400  A-
11338 MXU2.1 03:32:29.99 27:48:39.6 21.26 0 M-star 2 Early type
12519 46+47 03:32:31.51 27:40:59.9 20.14 0 M-star 2
12596 28+29 03:32:31.65 27:39:48.6 19.21 0 Star 2
12982 46+47 03:32:32.53 27:41:58.3 23.33 0.682 NELG 1 4400  A-
13046 86 03:32:32.72 27:48:59.5 22.35 0.669 NELG 1
13094 134 03:32:32.81 27:46:08.0 20.47 0.368 NELG 1
13106 84 03:32:32.86 27:41:55.8 24.27 0.948 NELG 1
14502 15 03:32:35.98 27:51:18.4 20.42 0.358 NELG 2 Not centered
14768 86 03:32:36.45 27:46:55.2 24.00 0.894 NELG 1 -9300  A
15210 46+47 03:32:37.37 27:41:26.2 20.66 0.670 gal 2 blended
15471 90 03:32:37.93 27:46:09.2 20.11 0.086 gal 2 reduction problem
15505 89 03:32:38.00 27:47:41.7 19.04 0 Star 2 Not centered
15773 86 03:32:38.59 27:46:31.6 21.96 0.625 gal 1
16089 89 03:32:39.16 27:48:44.6 19.68 0.457 gal 2
16647 15 03:32:40.37 27:55:38.2 23.55 0.350 NELG 1 Not centered
17281 15 03:32:41.64 27:51:57.6 21.30 0.783 gal 2
17312 46+47 03:32:41.72 27:40:07.7 23.76 0.761 NELG 1
17624 15 03:32:42.33 27:49:50.8 21.07 0.459 NELG 2 4100  A-
17660 MXU2.1 03:32:42.41 27:47:58.8 19.85 0 M-star 2
17958 84 03:32:43.03 27:43:59.9 21.73 0 M-star 2
18065 46+47 03:32:43.23 27:40:22.0 23.13 0.425 NELG 2
18365 90 03:32:43.82 27:46:05.5 17.71 0 Star 2
18468 89 03:32:44.03 27:48:24.3 19.01 0 Star 2
18473 89 03:32:44.06 27:51:43.3 19.19 0.305 NELG 1 Sky residuals
18474 46+47 03:32:44.06 27:40:48.2 23.43 0.730 gal 1
18545 134 03:32:44.20 27:47:33.5 21.96 0.738 NELG 2 6650  A-
18745 15 03:32:44.60 27:52:58.3 23.26 0.662 NELG 1 Not centered
18814 36+39+40 03:32:44.68 27:49:22.4 21.69 0.521 NELG 1 -8750  A
18894 36+39+40 03:32:44.86 27:47:27.2 18.82 0.215 NELG 2 Not centered, -8950  A
18894 89 03:32:44.87 27:47:27.6 18.82 0.213 NELG 2 Partly on slit
18981 137 03:32:45.02 27:54:39.6 19.55 0.459 NELG 2 6450  A-
18995 47 03:32:45.05 27:41:09.5 21.89 0.735 NELG 2
19026 36+39+40 03:32:45.05 27:47:38.3 20.36 0.346 NELG 2 -8900  A
19260 46 03:32:45.51 27:40:53.2 21.57 0.740 NELG 2
19633 46 03:32:46.24 27:41:23.9 23.14 0.638 NELG 2
19887 47 03:32:46.78 27:41:14.1 21.88 0.730 gal 2
19977 39+40 03:32:47.00 27:43:42.2 22.29 0.417 NELG 2

{ 85 {
Table 7|Continued
No mask  ô R z Class Qual Comments
(J2000) (J2000) (mag)
20803 46+47 03:32:48.65 27:44:33.3 22.92 0.215 NELG 2 5550  A-
20811 89 03:32:48.63 27:46:26.4 18.89 0.145 gal 2
20811 MXU2.1 03:32:48.63 27:46:26.4 18.89 0.147 gal 2
21088 90 03:32:49.20 27:44:36.3 19.81 0.217 NELG 2 3700  A-
21303 90 03:32:49.65 27:41:34.8 18.88 0 Star 2
21714 90 03:32:50.52 27:41:25.4 19.05 0.146 gal 2
21757 84 03:32:50.60 27:42:30.1 20.94 0.125 NELG 2
22083 46+47 03:32:51.28 27:44:29.4 20.77 0.534 gal 2 5100  A-
22439 146 03:32:52.05 27:44:29.8 21.80 0.821 NELG 1
22450 86 03:32:52.07 27:45:59.2 23.78 0.538 NELG 1
22471 89 03:32:52.12 27:51:08.9 20.40 0.128 NELG 2 3500  A-
22892 89 03:32:53.06 27:45:19.0 18.78 0.279 gal 2 3800  A-
22892 90 03:32:53.06 27:45:19.0 18.78 0.278 gal 2 5300  A-
23076 MXU2.1 03:32:53.45 27:48:29.6 18.40 0 Star 2
23256 90 03:32:53.92 27:41:09.9 18.93 0.146 NELG 2
23290 15 03:32:54.01 27:54:42.2 19.91 0.147 NELG 2
23307 86 03:32:54.02 27:47:04.5 22.05 0 M-star 2
23483 90 03:32:54.41 27:40:53.5 18.02 0.146 gal 2
23540 MXU2.1 03:32:54.51 27:46:16.2 18.36 0 Star 1 Bad sky subtraction
24034 46+47 03:32:55.58 27:43:22.5 19.27 0.146 NELG 2
24251 90 03:32:55.97 27:44:18.2 20.11 0 M-star 2 5500  A-
26135 86 03:32:58.89 27:45:30.3 23.19 1.035 NELG 1 Not centered
26822 36+39+40 03:33:01.24 27:49:42.4 21.35 0.512 gal 2 3800  A-
27022 36+39+40 03:33:02.76 27:43:16.1 16.75 0.129 gal 2 4400  A-, sky residuals
27511 36+39+40 03:33:07.10 27:46:39.7 18.29 0.220 gal 2 5800  A-, good signal, HELP!
27747 36+39+40 03:33:09.51 27:44:07.0 19.10 0.104 NELG 2 6700  A-, CHECK!
60014 99 03:31:59.33 27:43:02.4 20.50 0 M-star 2 4700  A-
60017 99 03:31:57.85 27:42:45.3 21.10 0.670 gal 2
60019 99 03:31:57.37 27:42:39.4 20.66 0.667 NELG 2 4350-
60021 99 03:31:56.42 27:40:45.9 18.75 0 M-star 2
60024 99 03:31:50.96 27:41:16.1 22.00 0.253 NELG 1
60028 99 03:31:49.02 27:39:45.7 N/A 0.813 NELG 1
60029 99 03:31:45.03 27:40:56.5 N/A 0.421 NELG 1 Sky residuals
60033 MXU11.1 03:31:45.91 27:51:30.7 21.88 0.681 NELG 2
60035 MXU11.1 03:31:44.63 27:50:52.3 20.76 0.523 NELG 2
60036 MXU11.1 03:31:57.25 27:52:22.7 21.27 0 M-star 2
60037 MXU11.1 03:31:54.08 27:55:01.9 20.82 0 Star 2
60038 MXU11.1 03:31:47.10 27:53:26.4 20.92 0 Star 2
60039 MOS11.1 03:32:04.53 27:50:07.4 19.90 0.229 NELG 2
60041 MXU11.1 03:31:49.82 27:48:36.6 19.07 0.182 NELG 2
Note. | See Section 9 for explanation of columns.

{ 86 {
Table 8. Comparision of the optical and X-ray classication.
BLAGN HEX LEX ABS
X-ray AGN-1 and QSO-1 31 5 10 1
X-ray AGN-2 and QSO-2 1 16 24 8
X-ray galaxy 0 3 20 12
Note. | Only the reliable identications are shown.

{ 87 {
Table 9. Optical counterparts not observed in our program.
No  ô R R-K HR
(J2000) (J2000) (mag) (mag)
Additional counterpart candidates
17a 03:32:49.17 27:55:04.6 24.59 - -0.41
17b 03:32:49.31 27:55:06.7 25.00 - -0.41
70c 03:32:01.21 27:46:47.4 24.31 - 0.47
86b 03:32:33.85 27:45:18.4 24.62 4.62 -0.05
96b 03:32:20.71 27:52:22.9 25.00 - -0.39
101b 03:32:55.48 27:47:53.4 24.61 4.20 -0.43
124c 03:32:02.61 27:45:24.9 25.49 - -1.00
189a 03:32:45.90 27:42:13.4 25.09 - 1.00
189b 03:32:45.80 27:42:11.3 25.40 - 1.00
189c 03:32:45.78 27:42:12.2 24.21 - 1.00
201a 03:32:39.05 27:44:39.7 26.11 - -0.06
205a 03:32:17.11 27:41:36.9 25.99 5.49 0.16
217a 03:32:33.10 27:52:05.9 - - -1.00
224b 03:32:28.82 27:46:21.6 25.04 - -1.00
239c 03:32:36.09 27:51:28.3 25.00 - -0.27
257c 03:32:13.49 27:48:55.1 25.64 - 0.35
268b 03:32:49.31 27:40:48.4 24.58 - 1.00
511c* 03:32:36.65 27:46:31.2 23.83 4.68 -0.24
511d* 03:32:36.42 27:46:31.6 23.61 4.50 -0.24
522c* 03:32:21.49 27:55:51.6 24.15 - -0.34
543b 03:31:56.92 27:51:00.6 24.52 - 0.17
547b 03:31:50.43 27:52:36.8 25.90 - 0.24
547c 03:31:50.27 27:52:35.9 24.81 - 0.24
553b 03:32:56.71 27:53:19.2 21.52 2.59 -1.00
577b 03:32:36.35 27:49:33.1 26.31 6.12 -1.00
585b 03:31:55.44 27:50:30.1 23.74 2.84 -1.00
590b 03:32:07.18 27:51:31.0 26.05 - -1.00
606b 03:32:24.91 27:50:10.0 26.13 - 1.00
620b 03:32:30.26 27:53:06.4 23.04 - -1.00
623b 03:32:28.55 27:46:58.8 25.23 4.72 -1.00
Inside the 8 arc min circle
48 03:32:24.85 27:56:00.1 24.55 4.79 -0.03
58 03:32:11.80 27:46:28.3 26.00 4.77 -0.36
72a 03:31:58.27 27:50:42.1 26.07 5.82 -0.23
133 03:32:02.49 27:44:29.6 - - 0.00
146 03:32:47.20 27:53:36.5 24.40 - -0.01
159 03:32:50.15 27:52:52.0 23.30 4.25 -0.30
210 03:32:38.35 27:55:53.6 - K=19.75 -0.45
226 03:32:04.46 27:46:43.3 - - -0.43

{ 88 {
Table 9|Continued
No  ô R R-K HR
(J2000) (J2000) (mag) (mag)
227 03:32:05.37 27:46:44.5 26.67 6.94 0.55
232 03:31:55.83 27:49:21.5 24.14 5.84 -1.00
240* 03:32:59.04 27:51:40.4 25.00W 5.80 -0.15
265 03:32:33.31 27:42:36.4 - K=20.32 0.47
507a* 03:33:00.14 27:49:23.2 22.86 1.65 0.10
507b* 03:32:59.92 27:49:24.1 24.51 - 0.10
508 03:32:51.69 27:52:13.5 - - 0.33
510 03:32:38.79 27:51:21.7 25.42 99.00 0.28
529a* 03:32:16.41 27:55:24.3 23.79 - 0.11
529b* 03:32:16.10 27:55:27.4 23.17 3.22 0.11
532 03:32:14.07 27:42:30.3 24.59 - -0.06
536 03:32:10.76 27:42:34.7 19.39 3.69 -0.25
537 03:32:09.85 27:50:15.3 - - 0.02
544* 03:31:54.48 27:51:05.5 24.18 4.53 0.05
546 03:31:52.33 27:47:53.0 25.12W 5.64 -0.15
555 03:32:37.96 27:53:07.9 25.41 - -1.00
556 03:32:00.43 27:52:28.8 22.09 4.25 -1.00
557 03:32:38.13 27:43:58.5 25.44 - -1.00
558 03:31:58.16 27:44:59.7 21.18W 4.05 -1.00
559 03:32:57.14 27:45:34.7 17.94 2.41 -1.00
564 03:32:16.63 27:46:36.7 26.04 - -1.00
571 03:33:03.75 27:48:10.4 26.14 5.80 -1.00
574 03:32:31.56 27:48:53.9 24.33 4.36 -1.00
578a 03:32:48.56 27:49:34.5 24.43 5.59 -1.00
578b 03:32:48.41 27:49:36.2 25.75 - -1.00
589 03:32:25.80 27:51:20.4 - - -1.00
592 03:32:47.18 27:51:47.6 23.54 4.64 -1.00
605 03:32:39.18 27:48:32.4 25.30 4.05 1.00
607 03:31:59.54 27:50:20.0 23.77 4.54 1.00
614 03:32:34.58 27:40:40.5 - K=19.97 0.02
618 03:32:29.35 27:56:19.4 25.57W - -1.00
622a 03:32:50.01 27:44:07.2 24.20 - -1.00
622b 03:32:50.01 27:44:05.4 25.38 - -1.00
625 03:32:00.92 27:47:57.0 21.68 4.31 -1.00
628 03:32:55.50 27:51:06.5 16.79 3.59 -1.00
629 03:32:53.33 27:51:04.6 25.26 - -1.00
632 03:32:33.45 27:52:27.8 - - 1.00
637 03:32:25.65 27:43:31.6 - - 1.00
639 03:32:52.63 27:42:39.24 23.36 4.91 1.00
902 03:32:22.07 27:51:12.2 26.15 - +1.00
903 03:32:25.84 27:40:47.8 23.07 3.90 -1.00
Outside the 8 arc min circle

{ 89 {
Table 9|Continued
No  ô R R-K HR
(J2000) (J2000) (mag) (mag)
3 03:33:05.90 27:46:50.6 - - -0.14
9 03:33:00.76 27:55:20.6 23.53 4.43 -0.57
35 03:32:34.43 27:39:13.2 24.32 5.60 -0.07
69a 03:32:01.46 27:41:39.2 24.02 4.61 -0.26
69b 03:32:01.52 27:41:40.5 23.90 - -0.26
174 03:33:01.21 27:44:20.9 25.37 7.21 0.05
179 03:31:49.50 27:50:34.0 - - -0.34
203 03:32:26.67 27:40:13.6 23.53 3.25 -0.29
213a 03:32:00.58 27:53:53.5 25.65 - -0.08
213b 03:32:00.37 27:53:53.3 25.06 - -0.08
213c 03:32:00.43 27:53:56.2 24.20 - -0.08
219 03:31:50.43 27:51:52.1 - K=19.94 -0.32
244 03:32:04.33 27:40:27.0 25.29 - -1.00
246 03:32:22.86 27:39:36.8 20.73 2.15 -0.24
501 03:33:10.19 27:48:42.1 22.99 NA -0.38
502 03:33:08.17 27:50:33.3 21.21 4.13 0.26
503 03:33:07.62 27:51:27.1 23.26 3.60 -0.41
504 03:33:05.67 27:52:14.5 18.96 3.31 0.18
505a 03:33:04.81 27:47:31.9 25.48 6.23 0.33
505b 03:33:04.96 27:47:33.3 24.64 - 0.33
506 03:33:02.99 27:51:47.0 - - -0.49
520 03:32:25.93 27:39:27.6 23.18 - -0.17
548a 03:31:44.85 27:51:59.3 24.85 - -0.42
548b 03:31:44.49 27:51:59.4 25.06 5.99 -0.42
568 03:33:11.07 27:47:34.4 - NA -1.00
576 03:31:44.19 27:49:26.4 - NA -1.00
597 03:32:51.36 27:55:43.7 24.69 5.46 1.00
608 03:33:03.87 27:50:26.2 20.74 3.17 1.00
613 03:32:24.55 27:40:10.4 23.13 4.59 1.00
636 03:31:50.40 27:50:42.0 - K=19.83 1.00
649 03:32:24.76 27:38:50.7 - NA -1.00
650 03:33:07.31 27:44:32.7 17.40 2.93 -1.00
653a 03:33:03.72 27:44:12.2 25.04 5.31 1.00
653b 03:33:03.82 27:44:11.7 26.20 - 1.00
653c 03:33:03.74 27:44:11.0 - K=19.63 1.00
Objects not covered by our imaging survey
2 03:33:08.81 27:42:54.8 22.84W 3.85 -0.65
7 03:33:01.68 27:58:17.8 20.26W NA -0.34
8 03:33:01.51 27:41:42.3 23.43W 4.66 -0.07
29 03:32:38.95 27:57:01.1 18.74W 3.21 0.39
40 03:32:29.02 27:57:30.6 20.82W 4.43 -0.34
74 03:31:57.82 27:42:09.0 22.06W 4.57 -0.26

{ 90 {
Table 9|Continued
No  ô R R-K HR
(J2000) (J2000) (mag) (mag)
183 03:32:34.12 27:56:40.5 - - 1.00
208 03:31:52.57 27:46:42.7 21.39W 3.95 -0.39
225 03:31:49.43 27:46:34.4 22.31W 3.07 -0.31
509 03:32:42.20 27:57:54.0 - NA -0.07
517 03:32:30.15 28:00:21.6 21.88W NA -0.21
533 03:32:13.87 27:56:01.2 - - 0.17
545 03:31:54.40 27:41:59.3 24.39W 3.89 0.32
550 03:33:00.71 27:57:48.2 24.28W NA -1.00
551 03:32:16.16 27:56:44.4 22.46W 2.19 -1.00
562 03:31:51.39 27:45:53.7 26.03W - -1.00
569 03:31:48.06 27:48:02.2 24.49W 4.39 -1.00
596 03:32:31.88 27:57:14.0 25.22W 5.79 1.00
604 03:31:48.62 27:47:15.0 26.56W 6.56 1.00
616 03:32:25.49 27:58:42.4 - NA -1.00
617 03:32:31.44 27:57:26.5 21.37W 4.08 -1.00
641 03:32:39.06 27:59:17.0 - NA 0.14
644 03:32:45.98 27:57:45.9 16.74W 2.51 -1.00
648 03:32:46.56 27:57:13.5 - K=16.91 -1.00
651 03:32:28.47 27:58:09.1 18.97W NA -1.00
Note. | For objects not covered by our FORS imaging survey,
the WFI magnitudes are given (Giacconi et al. 2002), indicated by
`W'. If the object is only detected in the K-band, the K magnitude
(Vega) is given instead of the R-K color. No detection in the K-band
images are indicated by a dash in the R-K column, no coverage is
indicated by `NA'.

{ 91 {
Table 10. Success rate of our spectroscopic survey.
Sample All sources R<24 sample
Total Observed Secure Total Observed Secure
All X-ray sources 345/416 247/277 133/141 195/214 157/170 118/126
Sources covered by our imaging survey 322/393 246/276 132/140 180/199 156/169 117/125
Sources covered by our spectroscopic survey 314/385 245/275 131/139 177/196 155/168 116/124
Inner 8 arc min circle 229/274 182/201 107/112 132/147 119/128 95/100
Note. | Both the number of X-ray objects (rst number) and the number of optical counterpart candidates (second
number) are given. X-ray objects with at least one R<24 optical counterpart candidate were considered part of the
R<24 sample. Secure identications include external identications. The four clusters (XID 249, 566, 594 and 645)
are not included.

{ 92 {
Table 11. The number of objects in dierent object classes
Object class z  2 z > 2
AGN-1 26/5 5/0
AGN-2 41/41 1/1
QSO-1 12/0 5/2
QSO-2 1/0 7/2
Galaxy 28/5 0
Cluster 5/1 0
Star 7 NA
Note. | For the AGN/QSO
object classes, both secure
(rst number) and unsecure
(second number) identica-
tions are counted.