K-Band Properties of Well-Sampled Groups of Galaxies

We use a sample of 55 groups and six clusters of galaxies ranging in mass from 7 × 10 11 to 1.5 × 10 15 M ⊙ to examine the correlation of the K s -band luminosity with mass discovered by Lin and coauthors in 2003. We use the Two-Micron All-Sky Survey catalog and published redshifts to construct complete magnitude-limited redshift surveys of the groups. From these surveys we explore the IR photometric properties of groups members, including their IR color distribution and luminosity function. Although we find no significant difference between the group K s luminosity function and the general field, there is a difference between the color distribution of luminous group members and their counterparts (generally background) in the field. There is a significant population of luminous galaxies with H - K s ≳ 0.35, which are rarely, if ever, members of the groups in our sample. The most luminous galaxies that populate the groups have a very narrow range of IR color. Over the entire mass range covered by our sample, the K s luminosity increases with mass as L ∝ M 0.64±0.06 , implying that the mass-to-light ratio in the K s band increases with mass. The agreement between this result and earlier investigations of essentially nonoverlapping sets of systems shows that this window in galaxy formation and evolution is insensitive to the selection of the systems and to the details of the mass and luminosity computations.