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: http://www.sao.ru/cats/doc/LCRS.html
Дата изменения: Wed Mar 18 12:25:11 2015 Дата индексирования: Sun Apr 10 00:26:38 2016 Кодировка: Поисковые слова: ngc 6520 |
=1996ApJ...470..172S
ADC_Keywords: Redshifts ; Galaxy catalogs ; QSOs
Keywords: cosmology: observations - galaxies: clusters: general -
galaxies: distances and redshifts - surveys
See also: See also the LCRS home pages at:
http://manaslu.astro.utoronto.ca/~lin/lcrs.html
http://www.aip.de:8080/~tucker/lcrs-mirror.html
Abstract:
The Las Campanas Redshift Survey (LCRS) consists of 26,418 redshifts
of galaxies selected from a CCD-based catalog obtained in the R band.
The survey covers over 700deg^2 in six strips, each 1.5x80deg, three
each in the north and south Galactic caps. The median redshift in the
survey is about 30,000km/s. Essential features of the galaxy selection
and redshift measurement methods are described and tabulated here.
These details are important for subsequent analysis of the LCRS data.
Two-dimensional representations of the redshift distributions reveal
many repetitions of voids, on the scale of about 5000km/s, sharply
bounded by large walls of galaxies as seen in nearby surveys.
Statistical investigations of the mean galaxy properties and of
clustering on the large scale are reported elsewhere. These include
studies of the luminosity function, power spectrum in two and three
dimensions, correlation function, pairwise velocity distribution,
identification of large-scale structures, and a group catalog.
Description:
In referencing individual galaxies within the LCRS, it is recommended
that investigators adhere to the IAU-registered LCRS naming
convention, as listed in the online "dictionary of nomenclature of
celestial objects" (http://astro.u-strasbg.fr/cgi-bin/Dic), which is:
LCRS BHHMMSS.s-DDMMSS, in which the coordinates are equinox 1950.0, RA
is truncated (* not rounded *) to a tenth of a second, and DEC is
truncated (* not rounded *) to a whole arcsecond.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fields 122 289 LCRS spectroscopic fields (Table 2)
catalog 98 82360 Redshift catalog (Table 3)
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Byte-by-byte Description of file: fields
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Bytes Format Units Label Explanations
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1- 8 A8 --- Field Field designation (1)
10- 11 I2 h RA1h First boundary field right ascension (1950.0)
13- 14 I2 min RA1m First boundary field right ascension (1950.0)
16- 20 F5.2 s RA1s First boundary field right ascension (1950.0)
22- 23 I2 h RA2h Second boundary field right ascension (1950.0)
25- 26 I2 min RA2m Second boundary field right ascension (1950.0)
28- 32 F5.2 s RA2s Second boundary field right ascension (1950.0)
34 A1 --- DE1- First boundary field declination sign
35- 36 I2 deg DE1d First boundary field declination (1950.0)
38- 39 I2 arcmin DE1m First boundary field declination (1950.0)
41- 44 F4.1 arcsec DE1s First boundary field declination (1950.0)
46 A1 --- DE2- Second boundary field declination sign
47- 48 I2 deg DE2d Second boundary field declination (1950.0)
50- 51 I2 arcmin DE2m Second boundary field declination (1950.0)
53- 56 F4.1 arcsec DE2s Second boundary field declination (1950.0)
58- 62 F5.2 mag m1 Lower limit magnitude (2)
64- 68 F5.2 mag m2 Higher limit magnitude (2)
70- 74 F5.2 mag mcen Faint central magnitude limit at m2 (2)
76- 78 I3 --- Nfib Designates whether data was obtained with
the 50- or 112-object spectrograph system
80- 82 I3 --- Ngal Number of galaxies, within the geometric and
photometric limits of the field, which
have redshifts.
84- 87 F4.2 --- f Sampling fraction (3)
89- 96 A8 "DD/MM/YY" Night Spectroscopic observations date
98-100 I3 --- Frame Spectroscopic exposure number
102-121 A20 --- plate Spectroscopic plate designation
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Note (1): "W", "E", or "M" means west, east, or middle,
Note (2): Photometric selection limits. Note the catalogs always contain
objects outside the photometric limits.
Isophotal magnitude m and central magnitude m_c_ of each galaxy
must meet the photometric selection criteria m1 <= m < m2
and m_c_ < m_cen_ - 0.5(m2-m)
Note (3): Fraction of objects (galaxies plus stars) with velocities, among
those objects meeting the photometric selection limits.
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Byte-by-byte Description of file: catalog
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Bytes Format Units Label Explanations
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1- 8 A8 --- Field Field designation
10- 15 F6.1 --- p Photometric catalog object number
17- 21 F5.2 mag mag Isophotal magnitude
23- 32 A10 --- Scan Designation of drift scan used to obtain object
photometry
34- 38 F5.2 mag mc Central magnitude
40- 41 I2 h RAh Right Ascension (1950.0)
43- 44 I2 min RAm Right Ascension (1950.0)
46- 50 F5.2 s RAs Right Ascension (may be 60.00) epoch 1950.0
52 A1 --- DE- Declination sign
53- 54 I2 deg DEd Declination (1950.0)
56- 57 I2 arcmin DEm Declination (1950.0)
59- 62 F4.1 arcsec DEs Declination (may be 60.0) epoch 1950.0
64- 66 A3 --- s ? Spectroscopic fiber designation (1)
68- 69 A2 --- type ? Spectrum type (1) (2)
71- 75 I5 km/s cz ? Heliocentric velocity (1)
77- 80 I4 km/s e_cz ? rms uncertainty on cz
82- 86 F5.3 --- sf ? Product of sampling fraction, apparent magnitude
completeness, and central surface brightness
completeness factors (1) (3)
88- 92 F5.3 --- gsf ? Same as sf but sampling fraction is computed
only in a 1000"-radius neighborhood of the
galaxy (1) (4)
94- 98 I5 km/s cz55 ? Instrumental constraints prevent two object
fibers from approaching closer than 55"
on the sky (1) (5)
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Note (1): Columns "s" to "cz55" are blank if not applicable to a particular
object
Note (2): Spectrum type.
- c, e, b: galaxy
- c: velocity from cross-correlation only
- e: velocity from emission-line fitting only
- b: velocity from both c and e
- *: star
- ?: spectrum failed to yield redshift
- nh, tc, bl: same as no spectrum attempted
(intended spectrum not observed)
- QS: QSO
- PN: planetary nebula
Note (3): See Lin et al. (1996ApJ...464...60L) for more information;
sf = f * F * G in the notation of that paper.
Objects should be weighted by 1/sf in statistical analyses.
Only those galaxies meeting the photometric selection limits have
an entry.
Note (4): This attempts to account for any variable geometric sampling effects,
e.g. the reduced spectroscopic success at field corners
(Shectman et al. 1995, in Wide-Field Spectroscopy and the Distant
Universe, proceedings of the 35th Herstmonceux Conference
(July 1994), eds. S. J. Maddox & A. Aragon-Salamanca
(Singapore: World Scientific), p. 98.).
Experience with the galaxy power spectrum (Lin et al.,
1996ApJ...471..617L) shows that using gsf instead of sf makes little
difference, but it does not hurt to check this for your own analyses.
Note (5): For an object without a redshift, cz55 is the velocity of its closest
neighbor within 55", if one exists, that has a velocity. Only objects
within the photometric limits have an entry. To assess the
significance of this selection effect for your particular analysis,
you can try assigning fake velocities as described in
Lin et al. (1996ApJ...471..617L).
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Origin: AAS CD-ROM series, Volume 7, 1996 Lee Brotzman [ADS] 22-Oct-96
================================================================================
(End) Patricia Bauer, [CDS] 03-Feb-1997