▪ Abstract ROSAT observations indicate that approximately half of all nearby groups of
galaxies contain spatially extended X-ray emission. The radial extent of the X-ray emission …

▪ Abstract Compact groups of galaxies have posed a number of challenging questions.
Intensive observational and theoretical studies are now providing answers to many of these …

We analyze the ur color distribution of 24,346 galaxies with M r≤-18 and z< 0.08, drawn
from the Sloan Digital Sky Survey first data release, as a function of luminosity and …

Numerous methods for finding clusters at moderate to high redshifts have been proposed in
recent years, at wavelengths ranging from radio to X-rays. In this paper we describe a new …

Massive early-type galaxies represent the modern day remnants of the earliest major star
formation episodes in the history of the universe. These galaxies are central to our …

We use cosmological gas dynamic simulations to investigate the accuracy of galaxy cluster
mass estimates based on X-ray observations. The experiments follow the formation of …

We present a catalog of 203 clusters of galaxies serendipitously detected in 647 ROSAT
PSPC high Galactic latitude pointings covering 158 deg 2. This is one of the largest X-ray …

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 …

Recently a number of studies have found a similarity between the passive fraction of central
and satellite galaxies when controlled for both stellar and halo mass. These results suggest …

Abstract The Group Evolution Multiwavelength Study (GEMS) involves a multiwavelength
study of a sample of 60 galaxy groups, chosen to span a wide range of group properties …