Compact groups are associations of a few galaxies in which the environment plays an important role in galaxy evolution. The low group velocity dispersion favors tidal interactions and mergers, which ...may bring stars from galaxies to the diffuse intragroup light. Numerical simulations of galaxy clusters in hierarchical cosmologies show that the amount of the diffuse light increases with the dynamical evolution of the cluster. We search for diffuse light in the galaxy group HCG 44 in order to determine its luminosity and luminosity fraction. Combining with literature data, we aim to constrain the dynamical status of Hickson compact groups. We use Intra Group planetary nebulae (IGPNe) as tracers of diffuse light. These are detected by the so-called on band-off band technique. We found 12 emission line objects in HCG 44, none of them associated with the galaxies of the group. 6/12 emission line objects are consistent with being IGPNe in HCG 44, but are also consistent with being Ly\(\alpha\) background galaxies. Thus we derive an upper limit to the diffuse light fraction in HCG 44 of 4.7%. We find a correlation between the fraction of elliptical galaxies and the amount of diffuse light in Hickson compact groups. Those with large fraction of diffuse light are those with large fractions in number and luminosity of E/S0 galaxies. We propose an evolutionary sequence for Hickson compact groups in which the amount of diffuse light increases with the dynamical evolution of the group.
We present surface photometry and stellar kinematics of a sample of 5 SB0 galaxies: ESO 139-G009, IC 874, NGC 1308, NGC 1440 and NGC 3412. We measured their bar pattern speed using the ...Tremaine-Weinberg method, and derived the ratio, R, of the corotation radius to the length of the bar semi-major axis. For all the galaxies, R is consistent with being in the range from 1.0 and 1.4, i.e. that they host fast bars. This represents the largest sample of galaxies for which R has been measured this way. Taking into account the measured distribution of R and our measurement uncertainties, we argue that this is probably the true distribution of R. If this is the case, then the Tremaine-Weinberg method finds a distribution of R which is in agreement with that obtained by hydrodynamical simulations. We compared this result with recent high-resolution N-body simulations of bars in cosmologically-motivated dark matter halos,and conclude that these bars are not located inside centrally concentrated dark matter halos.
Satellite accretion events have been invoked for mimicking the internal secular evolutionary processes of bulge growth. However, N-body simulations of satellite accretions have paid little attention ...to the evolution of bulge photometric parameters, to the processes driving this evolution, and to the consistency of this evolution with observations. We want to investigate whether satellite accretions indeed drive the growth of bulges, and whether they are consistent with global scaling relations of bulges and discs. We perform N-body models of the accretion of satellites onto disc galaxies. A Tully-Fisher (M \propto V_{rot}^ {alpha_TF}) scaling between primary and satellite ensures that density ratios, critical to the outcome of the accretion, are realistic. We carry out a full structural, kinematic and dynamical analysis of the evolution of the bulge mass, bulge central concentration, and bulge-to-disc scaling relations. The remnants of the accretion have bulge-disc structure. Both the bulge-to-disc ratio (B/D) and the Sersic index (n) of the remnant bulge increase as a result of the accretion, with moderate final bulge Sersic indices: n = 1.0 to 1.9. Bulge growth occurs no matter the fate of the secondary, which fully disrupts for alpha_TF=3 and partially survives to the remnant center for alpha_TF = 3.5 or 4. Global structural parameters evolve following trends similar to observations. We show that the dominant mechanism for bulge growth is the inward flow of material from the disc to the bulge region during the satellite decay. The models confirm that the growth of the bulge out of disc material, a central ingredient of secular evolution models, may be triggered externally through satellite accretion.
In this paper we analyze the structural parameters of the dwarf galaxies in the Coma cluster with \(-18 \le M_{B} \le -16\) and classify them in two types: those with surface brightness profiles well ...fitted by a single Sersic law were called dwarf ellipticals (dEs), and those fitted with Sersic-plus-exponential profiles were classified as dwarf lenticulars (dS0s). The comparison of the structural parameters of the dwarf galaxies in the Coma and Virgo clusters shows that they are analogous. Photometrically, the dE and dS0 galaxies in Coma are equivalent, having similar colors and global scales. However, the scale of the innermost parts (bulges) of dS0 galaxies is similar to the bulges of late-type spiral galaxies. In contrast, dEs have larger scales than the bulges of bright galaxies. This may indicate that dS0 and dE galaxies have different origins. While dE galaxies can come from dwarf irregulars (dIs) or from similar processes as bright Es, the origin of dS0 galaxies can be harassed bright late-type spiral galaxies.
We measured the bar pattern speed, \(\om\), of the SB0 galaxy NGC 1023 using the Tremaine-Weinberg (1984) method with stellar-absorption slit spectroscopy. The morphology and kinematics of the \hi ...gas outside NGC 1023 suggest it suffered a tidal interaction, sometime in the past, with one of its dwarf companions. At present, however, the optical disc is relaxed. If the disc had been stabilized by a massive dark matter halo and formed its bar in the interaction, then the bar would have to be slow. We found \(\om = 5.0 \pm 1.8\) \kmsa, so that the bar ends near its co-rotation radius. It is therefore rotating rapidly and must have a maximum disc.
We present broad-band photometry and provide a quantitative analysis of the
structure of galaxies in the inner region of the Abell Cluster 2443 (z~0.1).
The galaxy parameters have been derived by ...fitting a two-component model
(Sersic r^{1/n} bulge and exponential disk) to a magnitude-limited sample.
Using a new method of analysis which takes into account the effects of seeing
on the structural parameters and considers the ellipticity as an active
parameter, we avoid systematic errors arising from assumptions of circular
symmetry. 76% of the sample galaxies were classified with these models, the
rest were morphologically peculiar. For the spiral galaxies, the relation
between n and B/D is consistent with the trend observed in nearby field galaxy
samples. The Sersic index n (which can be considered as a concentration index)
of the elliptical galaxies is correlated with the local surface density of the
cluster. Monte Carlo simulations were used to check the reliability of the
method and determine the magnitude selection criteria.
We present a wide field \(V\)-band imaging survey of approximately 1 deg\(^2\) (\(\sim7.2 h^{-2}_{75}\) Mpc\(^{2}\)) in the direction of the nearby cluster of galaxies Abell 2151 (the Hercules ...Cluster). The data are used to construct the luminosity function (LF) down to \(M_V \approx -14.85\), thus allowing us to study the dwarf galaxy population in A2151 for the first time. The obtained global LF is well described by a Schechter function with best-fit parameters \(\alpha = -1.29^{+0.09}_{-0.08}\) and \(M_V^* = -21.41^{+0.44}_{-0.41}\). The radial dependence of the LF was investigated, with the faint-end slope tending to be slightly steeper in the outermost regions and farther away than the virial radius. Given the presence of significant substructure within the cluster, we also analysed the LFs in three different regions. We find that the dwarf to giant ratio increases from the northern to the southern subcluster, and from low to high local density environments, although these variations are marginally significant (less than 2\(\sigma\)).
The intracluster light (ICL) is a faint diffuse stellar component in clusters made of stars not bound to individual galaxies. We have carried out a large scale study of this component in the nearby ...Virgo cluster. The diffuse light is traced using planetary nebulae (PNe). The PNe are detected in the on-band image due to their strong emission in the OIII 5007 line, but disappear in the off-band image. The contribution of Ly-alpha emitters at z=3.14 are corrected statistically using blank field surveys. We have surveyed a total area of 3.3 square degrees in the Virgo cluster with eleven fields located at different radial distances. Those fields located at smaller radii than 80 arcmin from the cluster center contain most of the detected diffuse light. In this central region of the cluster, the ICL has a surface brightness in the range 28.8 - 30 mag per sqarsec in the B band, it is not uniformly distributed, and represents about 7% of the total galaxy light in this area. At distances larger than 80 arcmin the ICL is confined to single fields and individual sub-structures, e.g. in the Virgo sub-clump B, the M60/M59 group. For several fields at 2 and 3 degrees from the Virgo cluster center we set only upper limits. These results indicate that the ICL is not homogeneously distributed in the Virgo core, and it is concentrated in the high density regions of the Virgo cluster, e.g. the cluster core and other sub-structures. Outside these regions, the ICL is confined within areas of 100 kpc in size, where tidal effects may be at work. These observational results link the formation of the ICL with the formation history of the most luminous cluster galaxies.
We present surface photometry and stellar kinematics of NGC 4431, a barred dwarf galaxy in the Virgo cluster undergoing a tidal interaction with one of its neighbors, NGC 4436. We measured its bar ...pattern speed using the Tremaine-Weinberg method, and derived the ratio of the corotation radius, D_L, to the bar semi-major axis, a_B. We found D_L/a_B=0.6^{+1.2}_{-0.4} at 99% confidence level. Albeit with large uncertainty, the probability that the bar ends close to its corotation radius (i.e., 1.0 \leq D_L/a_B \leq 1.4) is about twice as likely as that the bar is much shorter than corotation radius (i.e., D_L/a_B > 1.4).
Mon.Not.Roy.Astron.Soc. 321 (2001) 269 The effects of seeing on the parameters of the S\`ersic profile are studied
in an analytical form using a Gaussian point spread function. The surface
brightness ...of S\`ersic profiles is proportional (in magnitudes) to $r^{1/n}$.
The parameter $n$ serves to classify the type of profile and is related to the
central luminosity concentration. It is the parameter most affected by seeing;
furthermore, the value of $n$ that can be measured is always smaller than the
real one. It is shown that the luminosity density of the S\`ersic profile with
$n$ less than 0.5 has a central depression, which is physically unlikely. Also,
the intrinsic ellipticity of the sources has been taken into account and we
show that the parameters are dependent when the effects of seeing are
non-negligible. Finally, a prescription for correcting raw effective radii,
central intensities and $n$ parameters is given.
