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INNER POLAR RINGS REGULAR LENTICULAR GALAXIES
1
K. Sil'chenko
2
Sternberg Astronomical Institute, 119992 Moscow, Russia; Isaac Newton Institute Chile, Moscow Branch; olga@sai.msu.su
Afanasiev
Special Astrophysical Observatory, 369167 Nizhnij Arkhyz, Russia; vafan@sao.ru
Received 2003 December accepted February
4
ABSTRACT
have investigated
a sample
of galaxies, mostly with circumnuclear dust lanes orthogonal their major
axes, chosen from Hubble Space Telescope Wide Field Planetary Camera
2 images. Two­dimensional spec­
troscopy undertaken with Multipupil Fiber Spectrograph telescope Special Astrophysical
Observatory Russian Academy Sciences revealed that indeed ionized centers these
eight lenticular galaxies rotate
in planes nearly orthogonal rotation symmetry) planes
of
central stellar components. Although almost galaxies located dense environments, external origin
rotation plane obvious because galaxies one known have extended
H
i disks,
in cases where angular resolution
H
i observations allows, orthogonality external
i
inner ionized disks. discuss
a possible relation inner gas polar rings
a triaxiality
of galactic
potential. stellar populations
in nuclei
of two galaxies are which excludes recent
formation bursts proves polar orbits circumnuclear rather stable. nuclei
of
NGC 2655 and NGC 4111, found signatures formation bursts some 1.5--2 Gyr ago. This finding
be related very central NGC 2655, which coplanar
to circumnuclear stellar radial
inflow NGC 4111; these reservoirs polar rings may responsible fueling nuclear
formation. words: galaxies: evolution galaxies: nuclei galaxies: structure
INTRODUCTION
Lenticular galaxies apparently similar
to elliptical gal­
axies concerning global properties their stellar pop­
ulations: they homogeneously red noticeable
present formation. However, unlike elliptical galaxies,
often possess
a modest amount
of ionized near their
centers; origin quite intriguing problem.
Large efforts solve problem have been applied
F. Bertola with collaborators. They come complex
conclusions. one hand, circumnuclear ionized gas
galaxies
is kinematically decoupled from stellar com­
ponent
in
at 40% cases, which implies
its external
origin (Bertola, Buson,
& Zeilinger 1992). other hand,
velocity dispersion circumnuclear ionized gas
matches well stellar velocity dispersion, sometimes over
extended areas, this evidence internal
origin, say, mass loss from bulge giant (Bertola
et 1995). Here, Bertola
et
al. (1995) make
a note: the latter
mechanism gas supply take place only when stars
ionized gas have coincident rotation
corotating.
is this condition
in necessary? There exist
some paths intrinsic secular dynamical evolution that may
orbit orientations course inflow toward
galactic center,
if belongs initially global
a galaxy rotates global symmetry plane
outer
of example, Friedli Benz (1993)
have calculated
a model self­consistent dynamical evolu­
a three­dimensional stellar­gaseous disk have
found that counterrotating belonging global disk
having antiparallel that the stars, finally
occupies stable orbits strongly inclined
to plane after
approaching center under driving force. resource
counterrotating may intrinsic: counterrotating stars
always present inside
a triaxial potential, they lost
would
be counterrotating. Nevertheless, nothing prohib­
external acquisition counterrotating
though must remember original spin orientation may
quite dissimilar present orientation
center galaxy. mention another possibility
considered detail Van Albada, Kotanyi, Schwarzschild
(1982).
If inner polar exists already within tum­
bling triaxial (stellar?) potential rotation
potential figure the orthogonal, outer parts
gaseous would become warped
by
#
the outermost would counterrotate stellar body.
even
if detect simultaneously inner polar and
counterrotating outer large­scale galactic disk,
would unable choose between them which primary,
the other.
In work, study sample lenticular galaxies with
inner polar rings. Traditionally, rings early­type
galaxies were treated result external accretion---
Kim (1989) about NGC 2768 NGC 4589. We
into doubt such interpretation inner
polar rings some galaxies large amount outer gas
1 Partly based observations collected with telescope
at
Special Astrophysical Observatory Russian Academy
of Sciences.
2 Guest investigator, Astronomy Centre.
2641
Astronomical Journal, 127:2641--2658, 2004
# American Astronomical Society. reserved. Printed U.S.A.

well settled main symmetry planes
of galaxies.
A
phenomenon inner polar rings spiral galaxies
firstly discovered
in nearby galaxy NGC 2841
(Sil'chenko, Vlasyuk,
& Burenkov 1997). Now we know
ready seven early­type spiral galaxies regular global
morphology inner polar rings---five found
and two more Corsini, Pizzella,
& Bertola (2002)
Corsini (2003). Concerning galaxies studied
noted inner gas polar rings spiral galaxies
often accompanied
a presence
of chemically distinct
(magnesium­enriched) nuclei that may treated remnants
secondary nuclear formation bursts, that they
always embedded into triaxial potential being
a global
NGC 4548 (Sil'chenko 2002a),
a mildly triaxial bulge,
NGC 2841 (Afanasiev Sil'chenko 1999),
a lenslike
inner stellar disk---perhaps remnant past
dissolved,
in NGC 7217 (Sil'chenko
& Afanasiev 2000).
However, according Corsini (2003), there galaxies
with inner polar where evidence triaxiality
compelling. How can orthogonal systems coexist? Does
it seem
more probable some intrinsic mechanisms, perhaps,
that described Friedli Benz (1993), could transfer
own galactic disk
a circumnuclear polar orbit?
what about inner polar rings S0's? have found
NGC (Afanasiev Sil'chenko 2000); appears
also inside
a kiloparsec­scale perhaps some
tion extremely young age nuclear stellar popu­
lation,
in bona red quiescent
lenticular galaxy. spectacular feature NGC 7280
predetermined discovery
of inner
in
galaxy: Hubble Space Telescope (HST
) Field Planetary
Camera (WFPC2) image center NGC 7280 revealed
that crossed stellar body very close
nucleus perpendicular major axis. examined
HST/WFPC2 images nearby lenticular galaxies
have found objects prominent circumnuclear
dust rings roughly orthogonal
to major axes inner
continuum isophotes. Among those, galaxies kine­
matical signatures inner gas polar rotation have been
claimed earlier from long­slit observations---in NGC 2768
Fried Illingworth (1994) and NGC 4111 Fisher (1997).
The seventh galaxy sample, NGC 3414,
ular central isophotes according WFPC2 (Rest
2001),
et
al. (2001) nevertheless found
a
lane center
by thorough analysis color distribution,
and orientation
of dust lane
is reported them
again orthogonal galactic major inner
polar eighth galaxy sample, NGC 2732,
is
prominent among others and have been detected
us rather occasionally. All eight galaxies
of sample,
with their global properties taken known extraga­
lactic databases, listed Table
have undertaken two­dimensional spectroscopy
samplegalaxieswith theMultipupilFiberSpectrograph (MPFS),
installed
at prime focus
6 telescope, inspect
things: stars ionized
in circumnuclear regions
these galaxies rotate indeed
in orthogonal planes, and
properties
of stellar populations, mean stellar
first affected some way presence unusual
subsystems
in centers. layout paper follows.
describe observations, data reduction, addi­
tional information which use analysis.
present results: descriptions individual galaxies, general
comparative kinematical analysis
of and ionized
centers sample galaxies, mean characteristics
nuclear stellar populations deduced comparing the measured
(and mapped) indices with evolutionary synthesis models.
Section contains some discussion results concerning
inner polar ring origin, possible role
of establishing
gas orbit orientation, also problem nuclear activity
fueling gas settled
in polar configurations.
a term
``nuclear activity'' includes
as nuclear star formation bursts,
well nonthermal compact nuclear sources.
2. OBSERVATIONS AND DATA REDUCTION
The spectral data analyze work obtained
mostly means two­dimensional spectroscopy. Integral
field spectroscopy
is
a rather new approach
proposed Professor Courtes some ago---for
a
TABLE
Global Parameters Galaxies
Parameter NGC 2732 2768 NGC 2911 NGC NGC 4111
(
a ................................... SAB(s)0/a
S0 S01/2 SB(r)0+ SA(s)0:
S0 SA(r)0+
R
25 (LEDA)
b (kpc) ...........................
B
0
T ....................................... 10.82 12.85 11.61 11.86 11.60
M
B (LEDA) ..................................... #20.96 #19.78 #21.11 #19.39 #20.79 #19.91 #19.34 #19.91
) (RC3) ................................ 0.83 0.94 0.96
(U #B)
0
T (RC3) ................................ 0.42 0.53 0.56
V
r
s
) ......................... 1404 1960 1414 2371
Distance
d .............................. 15.0
Inclination (LEDA) (deg) ...............
90
56
(LEDA) (deg).....................
95 174
v
rot (LEDA, from
H
i)
s
)
.
.
#
* (LEDA)
#1 )....................... 209
H i?..................................................
+
+
+
.
.
Nuclear source? .....................
.
. X­ray X­ray Radio Radio Radio
Environments .................................. Group Group Isolated Group Group Cluster Cluster
NASA /IPAC Extragalactic Database.
Lyon­Meudon Extragalactic Database.
Third Reference Catalogue Bright Galaxies.
distances NGC 2655, 2732,
are LEDA, distances
for 2768, 2787, 3414, 4111
et 2001.
SIL'CHENKO AFANASIEV
2642detailed description instrumental e.g., Bacon
et (1995).
It allows obtain simultaneously spectra
a wide spectral range point
of
an extended area
sky, example, from
a central
of
a galaxy. two­
dimensional array microlenses provides
a micro­
pupils, which onto entry spectrograph, and
having reduced full spectra corresponding
individual spatial elements, obtain
a fluxes
continuum emission line­of­sight velocities,
both stars and ionized absorption­line equiv­
alent widths, which usually expressed indices
well­formulated Lick system (Worthey
et 1994).
transformed into two­dimensional maps above
mentioned characteristics the central galaxy
studied. Besides panoramic view benefits,
approach gives
an unique opportunity overlay various two­
dimensional distributions other without diffi­
culties with positioning.
full spectral exposures obtained
sample galaxies given Table
2. Three different spectro­
graphs used.
two­dimensional spectroscopic observations
of 1998
January were made with variant MPFS
6
m telescope (Afanasiev
et 1990). panoramic view
provided
a microlenses array, and spec­
trum registered with CCD detector
of 580.
spatial scale was microlens. reciprocal
dispersion pixel with spectral resolution
8 slightly varying over the frame. variant
observations, also exposed separately
a blank
arcminutes from galaxy, because needed
subtraction
to calculate properly equivalent widths
absorption lines. The system Lick indices checked
observing standard stars from Worthey
et
(1994); found that index system coincided Lick
within
a mean deviation
Later 1998, new variant MPFS became opera­
tional prime focus telescope.
3 With respect
previous variant, MPFS
of view
increased and common spectral range larger due
to using
fibers: they transmit light from
; square elements
of
galaxy image
of spectrograph together with
additional fibers transmit sky background light
taken apart from galaxy, separate sky exposing
is not
necessary now.
of spatial element
is approxi­
mately
1
00
;
00
a 1024 1024 detector used. The
reciprocal dispersion 1.35 pixel
, with rather stable
spectral resolution
5 invert spectra
wavelength scale, expose separately
a spectrum
hollow cathod filled with helium, neon, and argon;
internal accuracy linearization was typically
8
green and
8
in red, additionally check
accuracy absence systematic velocity
measuring strong emission lines
i] k5577
[O
i] k6300. obtain MPFS data spectral
ranges: green one, covering 4700--5600 wavelength
interval, one, covering 6200--7000 interval. The
green spectra used calculate Lick indices Mg
Fe5270, and Fe5335, which suitable determine
metallicity, age, and ratio stellar populations
(Worthey 1994). They used cross­correlation with
a spectrum
a template usually
of III--K3 spectral
type, obtain line­of­sight velocity stellar com­
ponent map stellar velocity dispersion; typical
accuracy elementary stellar velocity determination km
s
. calibrate MPFS index system onto the stan­
Lick have observed
Worthey
al. (1994) during observational runs and
calculated linear regression formulae transform our
TABLE
2
Spectroscopy Galaxies Studied
Galaxy Exposure (minutes) Configuration (arcsec) (top) Spectral Range Seeing
(arcsec)
Oct NGC
60 BTA/MPFS+CCD
; 1024
;
15 4200--5600
Oct NGC
60 BTA/MPFS+CCD
; 1024
;
15 4200--5600
NGC
30 BTA/MPFS+CCD
; 1024
;
15 5800--7200
Oct NGC
60 BTA/MPFS+CCD
; 1024
;
15 4200--5600
Sep NGC
80 BTA/MPFS+CCD
; 1024
;
15 5800--7200
Oct NGC
15 BTA/MPFS+CCD
; 1024
;
15 4200--5600
Oct NGC
45 BTA/MPFS+CCD
; 1024
;
15 5800--7200
28.......... NGC
60 BTA/MPFS+CCD
; 1024
;
15 4200--5600
19.......... NGC
60 BTA/MPFS+CCD
; 4700--5450
19.......... NGC
60 BTA/MPFS+CCD
; 6200--6900
Oct NGC
30 BTA/MPFS+CCD
; 1024
;
15 5800--7200
Oct NGC
60 BTA/MPFS+CCD
; 1024
;
15 4200--5600
21.......... NGC
60 BTA/MPFS+CCD
; 6200--6900
22.......... NGC
45 BTA/SpN+CCD 1024
;
2
;
34 4500--5800
Dec NGC
75 BTA/MPFS+CCD
; 1024
;
15 4200--5600
22.......... NGC
30 BTA/SpN+CCD 1024
;
2
;
34 4500--5800
31.......... NGC
60 BTA/MPFS+CCD
; 1024
;
15 4200--5600
31.......... NGC
20 BTA/MPFS+CCD
; 1024
;
15 5800--7200
Mar
9 .......... NGC
90 BTA/MPFS+CCD
; 1024
;
15 5800--7200
29.......... NGC
45 BTA/MPFS+CCD
; 1024
;
15 4200--5600
Mar
9 .......... NGC
45 BTA/MPFS+CCD
; 1024
;
15 5800--7200
Mar NGC
60 BTA/MPFS+CCD
; 1024
;
15 4200--5600
Mar NGC
45 BTA/MPFS+CCD
; 1024
;
15 5800--7200
3 http://www.sao.ru/hq/lsfvo/devices/mpfs.
INNER POLAR RINGS 2643
5, 2004

instrumental index measurements into system;
rms scatters points linear dependencies about
0.2 indices under consideration within obser­
vational errors Worthey
et (1994). correct index
measurements stellar velocity dispersion, which
is
usually substantially nonzero the centers early­type
galaxies, have carried smoothing spectrum
standard 97907
a Gaussians various
widths; the derived dependencies index corrections
#
were approximated
by polynomials fourth order applied
measured index values before their calibrations into
Lick system. spectral range that contains strong
emission lines
[
N k6583 used derive line­of­
sight velocity fields ionized
To obtain gas veloc­
ities from the MPFS spectra, calculate wavelength bari­
centers emission lines, mostly
of
[ k6583, which
gives velocity accuracies 10--15
s
1998 January, observed two galaxies, NGC 2911
and NGC 3414, green spectral range with long­slit
spectrograph: called spectrophotometric complex
Nasmith­1 focus
of
m telescope (SpN) supplied with
Photometrics 1024
; used. Although
ciprocal dispersion these spectral observations was
same two­dimensional spectroscopy, pixel
,
narrower instrumental profile allowed
to analyze mul­
ticomponent velocity structure stellar and gaseous
circumnuclear components these galaxies applying
Gauss analysis
to emission­line and correlation­peak
profiles. structure
of central regions galaxies
under consideration compare some characteristic
entations with kinematical data, involve photometric
observational into analysis. give impression
global structures galaxies under consideration,
mostly Digitized Survey images, but Palma
Jacobus Kapteyn Telescope images retrieved Isaac
Newton Group (ING) Archive. reveal
a presence inner
dust/gas polar structures, HST/WFPC2 images:
available HST Archive galaxies
sample except NGC 2732. For NGC 2732, there public
photometric data sufficient quality,
so have undertaken
our observations focal reducer
6
m
scope Spectral Camera with Optical Reducer Photo­
metrical Interferometrical Observations (SCORPIO)
4
under rather good seeing conditions through broadband
VR­ and intermediate­band SED 755 filters; details
observations given Table
3.
In addition, sometimes
lucky retrieve HST/WFPC2 images both through
broadband narrowband filters---it case NGC
2768, NGC 2911, NGC 4111. these galaxies,
obtain maps pure gaseous emission H#+[N
subtracting broadband images properly normalized from
narrowband (F658N) images. Finally, obtain position
angles ellipticity
of innermost isophotes, applied
isophotal analysis reddest HST/WFPC2 images
galaxies (unfortunately, NGC 4111 HST/
NICMOS data), check additionally orientations
outer nodes, analyzed also R­images NGC
2768 from Digital Atlas
et (1996) NGC
3414 ING Archive---the latter minute expo­
sure image, strongly saturated center, which
obtained 1992 May the
1
m Jacobus Kapteyn Tele­
scope (JKT). data, both spectral photometric, except
obtained with MPFS, have reduced with
software produced Vlasyuk Special Astro­
physical Observatory (Vlasyuk 1993). Primary reduction
obtained with new MPFS was done IDL with
a
software created one indices
were calculated with FORTRAN program,
as
using FORTRAN program Vazdekis, which
provides index calculation.
RESULTS OBSERVATIONS
Since integral­field spectroscopy provides
dimensional line­of­sight velocity fields,
probe circularity rotation central structure
galaxies. have axisymmetric mass distribution
rotation
on circular orbits, direction
of maximum central
line­of­sight velocity gradient
it ``kinematical
major axis'') should coincide with nodes
as
photometric major does, whereas
a
of triaxial
potential isovelocities align with principal
of
lipsoid, and generally kinematical photometric major
axes diverge showing turns opposite sense respect
line nodes (Monnet, Bacon,
& Emsellem 1992;
Moiseev Mustsevoy 2000). simple cylindric
(disklike) rotation,
a convenient analytical expression
azimuthal dependence
of central line­of­sight velocity
gradients within area solid­body rotation:
r =dr
!
i cos (P:A:
);
where
!
is deprojected central angular rotation velocity,
i
inclination rotation plane, and P.A.
0 the
entation
of line nodes, coinciding case
axisymmetric ellipsoid
a thin disk) with photometric
major axis. fitting azimuthal variations central
line­of­sight velocity gradients with cosine curve, we
determine orientation kinematical major axis
phase the central angular rotation velocity
its ampli­
tude. This our main kinematical analysis.
The quantitative results this analysis applied
eight lenticular galaxies under consideration presented
Table
4 where we compare position angles
of outer
TABLE
Photometric Observations NGC 2732
Telescope Exposure Seeing (arcsec) (arcsec)
SCORPIO/BTA
1.8
SCORPIO/BTA
1.6
SCORPIO/BTA
1.7
http://www.sao.ru/ hq/moisav/scorpio/scorpio.html.
SIL'CHENKO AFANASIEV
2644isophotes
is, global disks' lines nodes), inner
isophote major axes,
of circumnuclear dust lane ori­
entations, emission­line intensity isophotes, with
kinematical major axes.
give some comments about how orientations
Table have been obtained. orientations lines
nodes some galaxies Table differ from P.A.
0 (phot)
Table this because updated Lyon­Meudon
Extragalactic Database's (LEDA) data: NGC 2655,
have taken NIR P.A.
0 from Mo˜ llenhoff Heidt (2001), and
NGC 2787, quite fresh estimate P.A.
0 from Erwin
Sparke (2003). orientations inner continuum iso­
photes
(it
is
a characteristics stellar component dis­
tributions) have been obtained
by averaging, over radius
range
00
, results isophote ellipse fitting
reddest avoid dust effect) and highest resolution images
among viewed
by orientations kinematical
major axes, both stars for gas, obtained
cosine fitting applied
to azimuthal variations
of line­of­
sight velocity gradients, described above. orientations
nuclear dust lanes taken mostly literature,
references given
in Table orientations
nitrogen emission­line intensity distributions estimated
rough visual inspection nitrogen emission maps, be­
cause small view
of MPFS and irregularities
emission­line isophotes prevent standard ellipse ap­
plication. P.A. estimates least precise
Table with
a typical
of
[
N
]
#
would describe the individual galaxies, and
summarize general impressions.
3.1. NGC 2655
Figure presents
a collection maps giant S0/a
galaxy. outer structure galaxy
is mysterious;
is included into the Atlas (1966). Obviously,
bulge­dominated: Baggett, Baggett,
& Anderson (1998) ap­
proximate full­range brightness profile single
Vaucouleurs' bulge and disk With
creasing photometry accuracy, outer been found,
parameters remain controversial: Mo˜llenhoff
& Heidt
(2001)
¼
76 0:4 from NIR
(JHK
) images, Erwin
& Sparke (2003), R­band
analysis, suggest almost face­on orientation (b=a 0:10,
i
), while measurements are quite uncertain.
00
00 isophote ellipticity profile almost
about 0:7, with P:A:
b
#
#
; however, what
meaning must attach the index ``b''? Erwin Sparke
(2003) doubt
it
is
a ``bar,'' agree: radius range
mentioned above well inside the bulge­dominated region.
Erwin Sparke (2003) right the galaxy
is seen almost
face­on, ellipticity within
00 may signify only
a triaxial bulge.
subtle inner structure, within
R
00
, deduced
solely from HST/F547M data. addition, one see
a noticeable polar (Fig. middle top). may
affect isophote parameter determination; case,
if
inner stellar disk well close face­on orientation
outer disk,
is hope catch photometric sig­
natures against luminous bulge background.
ionized kinematics, previously, from long­slit
observations, guessed that central region
of NGC 2655
something special (Sil'chenko
& Burenkov 1990),
velocity fields
in Figure (right column) revealed even
more complex picture than could suggest. Circumnuclear
rotate rigidly, with P:A:
# taking
count galaxy line­of­nodes orientation and approxi­
mate inner isophote P.A., conclude see axisymmetric
disklike (cylindric) stellar rotation. meantime, gas
kinematical major turns from
2
R
¼
4
00
6
00
; we suggest central ionized gas
rotates together with stars regular circumnuclear
disk?), only the ionized
at
R
00
6 related
polar ring and rotating plane strongly
clined the main symmetry plane galaxy. outer
border
of inner polar ring here marked quite
conventionally because, fact,
it
is beyond MPFS' field
view: our previous long­slit observations (Sil'chenko
Burenkov 1990) evidence polar rotation keeps
00 isophote the nitrogen emission
brightness corresponding
to polar location also
elongated north­south direction, orthogonally
continuum isophote elongation, agreement hy­
pothesis polar ring. Interestingly, extended
large­scale
i distribution shown NGC 2655 Erwin
Sparke (2003)
is elongated 110
#
# strictly
orthogonal rotation plane
00
6
. Does this
contradict their probable common formation external
accretion? index maps central part NGC 2655 rather
featureless. Earlier (Sil'chenko, Afanasiev, Vlasyuk
1992) reported absence chemically distinct nucleus
galaxy, and maps
of Figure
1 (bottom) seem con­
conclusion. Perhaps, unresolved mini­
mum
b center; real, signify either
TABLE
4
Orientation Parameters Galaxies
Parameters NGC 2732 NGC 2768 NGC NGC NGC NGC
P.A.
0 (deg)............
95
P.A.
*
,
2
#
2
#
2
3
#
P.A.
*
,
# 88.5
# (137)
#
2 324
#
#
3
3
P.A.
dust ........
a
.
. #175
b
d
e
e
P.A.
gas, (deg) 45!20(R
4
) #13
#
72
63
#
68
#
7
P.A.
[
N (deg) Round #80 Round Round
& Sparke
Bertola
et
al.
et 2003.
work. 2001.
f 1998.
INNER POLAR RINGS 2645
5, 2004

metal­deficient compact nucleus accreted globular
cluster?), which suppose
to quite improbable,
extreme youth the nuclear stellar population. Below
show latter
is
2732
This lenticular galaxy
is seen edge­on. Although bright
and nearby, has attracted attention other
members our sample;
in particular,
it lacks HST data.
However, ground­based investigations photometric
structure stellar kinematics undertaken. Both
Seifert Scorza (1996) and Baggett (1998), formers
basing two­dimensional photometric analysis
ters basing major­axis V­brightness profile decomposition,
have found global stellar the galaxy has
a
center, within
R
#
00
; such disk profiles often
met barred galaxies, although NGC 2732
is not classified
barred. Hence not expect find
a circumnuclear stellar
disk this galaxy. nuclear emission lines weak
confined
to central galaxy,
so
as know
gaseous kinematics 2732 were investigated
before work.
Our photometric obtained with reducer
6
telescope SCORPIO have revealed
a presence large
spots near minor
of edge­on galaxy (Fig.
middle); taking into account lack significant amount
gas galaxy (Haynes
et 1990), these off­plane
relatively recent formation quite strange. Two­
dimensional velocity fields stellar ionized
components (Fig. right column) solve puzzle partially.
The galaxy demonstrates orthogonal rotations stars
and
N
ii] emission isophotes elongated accordance
kinematical major axis, deal with inner
polar stars rotate quite axisymmetrically: although
isophote major bulge deviates from
nodes some
#
# ---it firm photometric conclusion,
full agreement with photometry Seifert
& Scorza
(1996)---the stellar kinematical major axis turns together
The stellar velocity dispersion demonstrates peak
center agrees with the absence circumnuclear stellar
disk. Obviously, stellar component which axisymmetric
rotation we observe bulge
of NGC 2732.
addition, absence circumnuclear stellar
NGC 2732 disfavors
a presence chemically distinct
cleus. Indeed, metal­line index distributions bottom)
rather flat, rather low levels galaxy's stellar
locity dispersion total luminosity.
2768
another galaxy
in sample, besides NGC 2655,
lacks perhaps
a global disk:
in some catalogs (e.g., RC3),
it
classified Kent (1985) fitted brightness profile
a
single Vaucouleurs' law, Peletier (1990) found
practically constant orientation
of isophote major
about
#
#
. However, have undertaken
our own isophote analysis images
1.---Maps
for 2655. row: Large­scale photographic view small­scale HST image, where selects
an observed
in
with MPFS. Bottom row
( from
to right):
of Lick indices hFei [#(Fe5270 Fe5335)/2]
of velocity dispersion; isophotes
show green continuum distribution. Right column
( bottom): Nitrogen­emission isophotes overlaid
red continuum gray­scaled velocity
fields ionized and
of
the component given isovelocities overlaid
the gray­scaled continuum distributions. orientation maps
is
same, northeast directions shown corner large­scale image.
SIL'CHENKO AFANASIEV
2646NGC 2768 retrieved from Digital Nearby Gal­
axies Frei
et (1996), have obtained persistent trend
isophote major axis P.A.
to optical border
galaxy, from
#
at
R
¼
00 P:A:
0
#
R
¼
00 variations isophote ellipticity not
quite smooth, having
a ``knee''
at maximum
R
¼
00 with
a subsequent even NGC 2768
spheroid, probably
a triaxial one.
In center NGC 2768, Fried
& Illingworth (1994)
reported polar rotation ionized
00
confro