Misc,
Mass growth and mergers: direct observations of the luminosity function of LRG satellite galaxies out to z=0.7 from SDSS and BOSS images
(2011)cite arxiv:1108.1392Comment: Submitted to ApJ.
Abstract
We present a statistical study of the luminosity functions of galaxies
surrounding luminous red galaxies (LRGs) at average redshifts <z>=0.34 and
<z>=0.65. The luminosity functions are derived by extracting source photometry
around the LRGs and subtracting foreground and background contamination using
randomly selected control fields. We show that at both studied redshifts the
average luminosity functions of the LRGs and their satellite galaxies are
poorly fitted by a Schechter function due to a luminosity gap between the
centrals and their most luminous satellites. We utilize a two-component fit of
a Schechter function plus a log-normal distribution to demonstrate that LRGs
are typically brighter than their most luminous satellite by roughly 1.3
magnitudes. This luminosity gap implies that interactions within LRG
environments are typically restricted to minor mergers with mass ratios of 1:4
or lower. The luminosity functions further imply that roughly 35% of the mass
in the environment is locked in the LRG itself, supporting the idea that mass
growth through major mergers within the environment is unlikely. Lastly, we
show that the luminosity gap may be at least partially explained by the
selection of LRGs as the gap can be reproduced by sparsely sampling a Schechter
function. In that case LRGs may represent only a small fraction of central
galaxies in similar mass halos.
