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VLT-FORS1 images of NGC 3258 and FS90 110 (left), and NGC 3268 and FS90 192 (right) (Bassino et al. 2008). North is up, and east to the left.
Source publication
We confirm the existence of two compact elliptical (cE) galaxies in the
cen- tral region of the Antlia cluster through MAGELLAN-MIKE and GEMINI-
GMOS spectra. Only about a dozen galaxies of this rare type are known
today up to a distance of 100 Mpc. With this finding, Antlia becomes the
nearest galaxy cluster harbouring more than one cE galaxy amon...
Context in source publication
Context 1
... this contribution we present two newly confirmed FS90 cE galaxies in Antlia (namely, FS90 110 and FS90 192). Each of them is close in projection to one of the giant ellipticals NGC 3258 and NGC 3268 (Fig. 1). A photometric analysis was presented in Paper II. In that work, both galaxies were considered as firm candidates to be genuine cEs due to their photometric characteristics, similar to those of confirmed cEs. It is interesting to find new members of this class in the nearby Universe as it has been proposed that cE galaxies are the ...
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Citations
As part of the SPLASH survey of the Andromeda (M31) system, we have obtained Keck/DEIMOS spectra of the compact elliptical (cE) satellite M32. This is the first resolved-star kinematical study of any cE galaxy. In contrast to most previous kinematical studies that extended out to r 30'' ~ 1 r
effI
~ 100 pc, we measure the rotation curve and velocity dispersion profile out to r ~ 250'' and higher order Gauss-Hermite moments out to r ~ 70''. We achieve this by combining integrated-light spectroscopy at small radii (where crowding/blending are severe) with resolved stellar spectroscopy at larger radii, using spatial and kinematical information to account statistically for M31 contamination. The rotation curve and velocity dispersion profile extend well beyond the radius (r ~ 150'') where the isophotes are distorted. Unlike NGC 205, another close dwarf companion of M31, M32's kinematics appear regular and symmetric and do not show obvious sharp gradients across the region of isophotal elongation and twists. We interpret M31's kinematics using three-integral axisymmetric dynamical equilibrium models constructed using Schwarzschild's orbit superposition technique. Models with a constant mass-to-light ratio can fit the data remarkably well. However, since such a model requires an increasing tangential anisotropy with radius, invoking the presence of an extended dark halo may be more plausible. Such an extended dark halo is definitely required to bind a half-dozen fast-moving stars observed at the largest radii, but these stars may not be an equilibrium component of M32.
We report the discovery of the second compact elliptical (cE) galaxy SDSS J150634.27+013331.6 in the nearby NGC 5846 group by the Virtual Observatory (VO) workflow. This object (MB=−15.98 mag, Re= 0.24 kpc) becomes the fifth cE where the spatially resolved kinematics and stellar populations can be obtained. We used archival HST WFPC2 images to demonstrate that its light profile has a two-component structure, and integrated photometry from GALEX, SDSS, UKIDSS and Spitzer to build the multiwavelength spectral energy distribution to constrain the star formation history (SFH). We observed this galaxy with the PMAS IFU spectrograph at the Calar-Alto 3.5-m telescope and obtained two-dimensional maps of its kinematics and stellar population properties using the full-spectral fitting technique. Its structural, dynamical and stellar population properties suggest that it had a massive progenitor heavily tidally stripped by NGC 5846.
As part of the SPLASH survey of the Andromeda galaxy (M31) and its neighbors,
we have obtained Keck/DEIMOS spectra of the compact elliptical (cE) satellite
M32. This is the first resolved-star kinematical study of any cE galaxy. In
contrast to previous studies that extended out to r<30"~1Re~100pc, we measure
the rotation curve and velocity dispersion profile out to r~250" and higher
order Gauss-Hermite moments out to r~70". We achieve this by combining
integrated-light spectroscopy at small radii (where crowding/blending are
severe) with resolved stellar spectroscopy at larger radii, using spatial and
kinematical information to statistically account for M31 contamination. The
rotation curve and velocity dispersion profile extend well beyond the radius
(r~150") where the isophotes are distorted. Unlike NGC 205, another close dwarf
companion of M31, M32's kinematic are regular and symmetric and do not show
obvious sharp gradients across the region of isophotal elongation and twists.
We interpret M32's kinematics using three-integral axisymmetric dynamical
equilibrium models constructed using Schwarzschild's orbit superposition
technique. Models with a constant M/L can fit the data remarkably well.
However, since such a model requires an increasing tangential anisotropy with
radius, invoking the presence of an extended dark halo may be more plausible.
Such an extended dark halo is definitely required to bind a half-dozen
fast-moving stars observed at the largest radii, but these stars may not be an
equilibrium component of M32. The observed regularity of the stellar
kinematics, as well as the possible detection of an extended dark halo, are
unexpected if M31 tides are significant at large radii. While these findings by
themselves do not rule out tidal models for cE formation, they suggest that
tidal stripping may not be as significant for shaping cE galaxies as has often
been argued.
(Abridge) We present a new analysis of the early-type galaxy population in
the central region of the Antlia cluster, focusing on the faint systems like
dwarf ellipticals (dE) and dwarf spheroidals (dSph). We confirm 22 early-type
galaxies as Antlia members, using GEMINI-GMOS and MAGELLAN-MIKE spectra. Among
them, 2 belong to the rare type of compact ellipticals (cE), and 5 are new
faint dwarfs that had never been catalogued before. In addition, we present 16
newly identified low surface brightness galaxy candidates, almost half of them
displaying morphologies consistent with being Antlia's counterparts of Local
Group dSphs, that extend the faint luminosity limit of our study down to MB =
-10.1 (BT = 22.6) mag. We built an improved CMR in the Washington photometric
system, i.e. integrated T1 magnitudes versus (C - T1) colours, which extends
\sim 4 mag faintwards the limit of spectroscopically confirmed Antlia members.
When only confirmed early-type members are considered, this relation extends
over 10 mag in luminosity with no apparent change in slope or increase in
colour dispersion towards its faint end. The intrinsic colour scatter of the
relation is compared with those reported for other clusters of galaxies; we
argue that it is likely that the large scatter of the CMR, usually reported at
faint magnitudes, is mostly due to photometric errors along with an improper
membership/morphological classification. The distinct behaviour of the
luminosity versus mean effective surface brightness relation at the bright and
faint ends is analyzed, while it is confirmed that dE galaxies on the same
relation present a very similar effective radius, regardless of their colour.
The projected spatial distribution of the member sample confirms the existence
of two groups in Antlia, each one dominated by a giant elliptical galaxy and
with one cE located close to each giant.
We use a combined 120 ks Chandra exposure to analyze X-ray edges produced by non-hydrostatic gas motions (sloshing) from galaxy collisions, and cavities formed by active galactic nucleus (AGN) activity. Evidence for gas sloshing is seen in the spiral morphology and multiple cold front edges in NGC 5846's X-ray surface brightness distribution, while the lack of spiral structure in the temperature map suggests that the perturbing interaction was not in the plane of the sky. Density and spectral modeling across the edges indicate that the relative motion of gas in the cold fronts is at most transonic. Evidence for AGN activity is seen in two inner bubbles at 0.6 kpc, filled with 5 GHz and 1.5 GHz radio plasma and coincident with Hα emission, and in a ghost bubble at 5.2 kpc west of NGC 5846's nucleus. The outburst energy and ages for the inner (ghost) bubbles are ~1055 erg and ~2 Myr (~5 × 1055 erg and 12 Myr), respectively, implying an AGN duty cycle of 10 Myr. The inner bubble rims are threaded with nine knots, whose total 0.5-2 keV X-ray luminosity is 0.3 × 1040 erg s–1, a factor ~2-3 less than that of the surrounding rims, and 0.7 keV mean temperature is indistinguishable from that of the rims. We suggest that the knots may be transient clouds heated by the recent passage of a shock from the last AGN outburst. We also observe gas stripping from a cE galaxy, NGC 5846A, in a 0.5 kpc long (~105M
☉) hot gas tail, as it falls toward NGC 5846.
We present two newly-discovered compact elliptical (cE) galaxies, exhibiting
clear evidence of tidal steams, and found during a search of SDSS DR7 for cE
candidates. The structural parameters of the cEs are derived using GALFIT,
giving effective radii, Re, of 388 and 263 parsecs, and B-band mean surface
brightnesses within Re of 19.4 and 19.2 magnitudes per arcsec squared. We have
re-analysed the SDSS spectra, which indicate that they possess young to
intermediate-age stellar populations. These two cEs provide direct evidence, a
"smoking gun", for the process of tidal stripping that is believed to be the
origin of M32-type galaxies. Both are in small groups with a large spiral
fraction, suggesting that we may be seeing the formation of such cE galaxies in
dynamically young environments. The more compact of the galaxies is found in a
small group not unlike the Local Group, and thus provides an additional model
for understanding M32.
