Related papers: Galaxy Groups
We describe the properties of a sample of galaxy groups with very unusual distributions of galaxy luminosities. The most extreme example has an X-ray luminosity similar to that of the Virgo cluster but has a very low richness, with only one…
We investigate the clustering of galaxy groups and clusters in the SDSS using the Berlind et al. (2006) group sample, which is designed to identify galaxy systems that each occupy a single dark matter halo. We estimate group masses from…
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than…
Low mass galaxies in the Local Group are dominated by dark matter and comprise the well studied ``dwarf Spheroidal" (dSph) class, with typical masses of $10^{9-10}M_\odot$ and also the equally numerous ``ultra faint dwarfs" (UFD),…
We use high resolution simulations to study the formation and distribution of galaxies within a cluster which forms hierarchically. We follow both dark matter and baryonic gas which is subject to thermal pressure, shocks and radiative…
We present results from a systematic investigation of the X-ray properties of a sample of moderate redshift (0.3<z<0.6) galaxy groups. These groups were selected not by traditional X-ray or optical search methods, but rather by an…
We find a strong correlation between the effective radius of the largest early-type galaxies in compact groups of galaxies and the velocity dispersion of the groups. The lack of a similar correlation for late type galaxies is supportive of…
We report a list of groups consisting of dwarf galaxies only. The sample contains 126 objects, mainly combined in pairs. The most populated group contains six dwarf galaxies. The majority of systems considered reside in the low-density…
We examine the relationship between the group x-ray luminosity in the 0.3-3.5 keV band and the measured velocity dispersion, and galaxy surface number density. We find definite correlations. Richer groups follow the same relation as rich…
The gap between first and second ranked galaxy magnitudes in groups is often considered a tracer of their merger histories, which in turn may affect galaxy properties, and also serves to test galaxy luminosity functions (LFs). We remeasure…
We study the mass-to-light ratio of galaxy systems from poor groups to rich clusters, and present for the first time a large database for useful comparisons with theoretical predictions. We extend a previous work, where B_j band…
We explore the shape of the galaxy luminosity function (LF) in groups of different mass by creating composite LFs over large numbers of groups. Following previous work using total group luminosity as the mass indicator, here we split our…
We are studying the mass distribution in a sample of 50 early type spiral galaxies, with morphological type betweens S0 and Sab and absolute magnitudes M_B between -18 and -22; they form the massive and high-surface brightness extreme of…
We present DEIMOS multi-object spectroscopy (MOS) of 22 star-forming dwarf galaxies located in four gas-rich groups, including six newly-discovered dwarfs. Two of the galaxies are strong tidal dwarf galaxy (TDG) candidates based on our…
Numerical simulations as well as optical and X-ray observations over the last few years have shown that poor groups of galaxies can evolve to what is called a fossil group. Dynamical friction as the driving process leads to the coalescence…
Since reionization prevents star formation in most halos below 3 x 10^9 solar masses, dwarf galaxies only populate a fraction of existing dark matter halos. We use hydrodynamic cosmological simulations of the Local Group to study the…
We consider seven distant galaxies with clearly evident spiral structure from HST images. Three of these were chosen from Vogt et al. (1996) (VFP) and have measured rotational velocities. Five were chosen from the Medium Deep Survey and are…
We study the radio emission of the most massive galaxies in a sample of dynamically relaxed and un-relaxed galaxy groups from Galaxy and Mass Assembly (GAMA). The dynamical state of the group is defined by the stellar dominance of the…
It is not well understood whether the growth of early-type cluster galaxies proceeds inside-out, outside-in, or at the same pace at all radii. In this work we measured the galaxy size, defined by the radius including 80\% of the galaxy…
We aim at defining homogeneous selection criteria of small galaxy systems in order to build catalogues suitable to compare main properties of pairs, triplets, and groups with four or more members. To this end we use spectroscopic and…