2,257 research outputs found
The compact group--fossil group connection: observations of a massive compact group at z=0.22
It has been suggested that fossil groups could be the cannibalized remains of
compact groups, that lost energy through tidal friction. However, in the nearby
universe, compact groups which are close to the merging phase and display a
wealth of interacting features (such as HCG 31 and HCG 79) have very low
velocity dispersions and poor neighborhoods, unlike the massive, cluster-like
fossil groups studied to date. In fact, known z=0 compact groups are very
seldom embedded in massive enough structures which may have resembled the
intergalactic medium of fossil groups. In this paper we study the dynamical
properties of CG6, a massive compact group at z=0.220 that has several
properties in common with known fossil groups. We report on new g' and i'
imaging and multi-slit spectroscopic performed with GMOS on Gemini South. The
system has 20 members, within a radius of 1 h_70^-1 Mpc, a velocity dispersion
of 700 km/s and has a mass of 1.8 x 10^14 h_70^-1 Msun, similar to that of the
most massive fossil groups known. The merging of the four central galaxies in
this group would form a galaxy with magnitude M_r' ~ -23.4, typical for
first-ranked galaxies of fossil groups. Although nearby compact groups with
similar properties to CG 6 are rare, we speculate that such systems occurred
more frequently in the past and they may have been the precursors of fossil
groups.Comment: 7 pages, 3 figures (one color, low resolution), uses emulateapj.sty.
Accepted for publication in ApJ Lette
Intra-group Light in Hickson Compact Groups
We have analyzed the intra-group light component of 3 Hickson Compact Groups
(HCG 79, HCG 88 and HCG 95) with detections in two of them: HCG 79, with
of the total band luminosity and HCG 95 with . HCG 88
had no component detected. This component is presumably due to tidally stripped
stellar material trapped in the group potential and represents an efficient
tool to determine the stage of dynamical evolution and to map its gravitational
potential. To detect this low surface brightness structure we have applied the
wavelet technique OV\_WAV, which separates the different components of the
image according to their spatial characteristic sizes.Comment: Small update on the associated institutions lis
Are compact groups hostile towards faint galaxies?
The goal of this work is to understand whether the extreme environment of
compact groups can affect the distribution and abundance of faint galaxies
around them. We performed an analysis of the faint galaxy population in the
vicinity of compact groups and normal groups. We built a light-cone mock galaxy
catalogue constructed from the Millennium Run Simulation II plus a
semi-analytical model of galaxy formation. We identified a sample of compact
groups in the mock catalogue as well as a control sample of normal galaxy
groups and computed the projected number density profiles of faint galaxies
around the first- and the second-ranked galaxies. We also compared the profiles
obtained from the semi-analytical galaxies in compact groups with those
obtained from observational data. In addition, we investigated whether the
ranking or the luminosity of a galaxy is the most important parameter in the
determination of the centre around which the clustering of faint galaxies
occurs. There is no particular influence of the extreme compact group
environment on the number of faint galaxies in such groups compared to control
groups. When selecting normal groups with separations between the 1st and 2nd
ranked galaxies similar to what is observed in compact groups, the faint galaxy
projected number density profiles in compact groups and normal groups are
similar in shape and height. We observed a similar behaviour of the population
of faint galaxies in observations and simulations in the regions closer to the
1st and 2nd ranked galaxies. Finally, we find that the projected density of
faint galaxies is higher around luminous galaxies,regardless of the ranking in
the compact group. The semi-analytical approach shows that compact groups and
their surroundings do not represent a hostile enough environment to make faint
galaxies to behave differently than in normal groups.Comment: 12 pages, 10 figures. Accepted for publication in Astronomy &
Astrophysic
Are compact groups hostile towards faint galaxies?
Aims: The goal of this work is to understand whether the extreme environment of compact groups (CGs) can affect the distribution and abundance of faint galaxies around them. Methods: We performed an analysis of the faint galaxy population in the vicinity of compact and normal groups. We built a light-cone mock galaxy catalogue constructed from the Millennium Run Simulation II plus a semi-analytical model of galaxy formation. We identified a sample of CGs in the mock catalogue as well as a control sample of normal galaxy groups and computed the projected number density profiles of faint galaxies around the first and the second ranked galaxies. We also compared the profiles obtained from the semi-analytical galaxies in CGs with those obtained from observational data. In addition, we investigated whether the ranking or the luminosity of a galaxy is the most important parameter in the determination of the centre around which the clustering of faint galaxies occurs. Results: There is no particular influence of the extreme compact group (CG) environment on the number of faint galaxies in such groups compared to control groups. When selecting normal groups with separations between the first and second ranked galaxies similar to what is observed in CGs, the faint galaxy projected number density profiles in CGs and normal groups are similar in shape and height. We observed a similar behaviour of the population of faint galaxies in observations and simulations in the regions closer to the first and second ranked galaxies. Finally, we find that the projected density of faint galaxies is higher around luminous galaxies, regardless of the ranking in the CG. Conclusions: The semi-analytical approach shows that CGs and their surroundings do not represent a hostile enough environment to make faint galaxies behave differently than in normal groups.Fil: Zandivarez, Arnaldo Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomia Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomia Teórica y Experimental; ArgentinaFil: Diaz, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomia Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomia Teórica y Experimental; ArgentinaFil: Oliveira, Claudia Mendes de. Universidade do Sao Paulo. Instituto Astronomia, Geofisica e Ciencias Atmosfericas; BrasilFil: Gubolin, Henrique. Universidade do Sao Paulo. Instituto Astronomia, Geofisica e Ciencias Atmosfericas; Brasi
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