RASS-SDSS Galaxy Cluster Survey. IV. A ubiquitous dwarf galaxy population in clusters

Astrophysics, abstract
astro-ph/0506201

From: Paola Popesso [view email]

Date: Thu, 9 Jun 2005 13:32:10 GMT   (168kb)

We analyze the Luminosity Functions (LFs) of a subsample of 69 clusters from
the RASS-SDSS galaxy cluster catalog. When calculated within the cluster
physical sizes, given by r200 or r500, all the cluster LFs appear to have the
same shape, well fitted by a composite of two Schechter functions with a marked
upturn and a steepening at the faint-end. Previously reported
cluster-to-cluster variations of the LF faint-end slope are due to the use of a
metric cluster aperture for computing the LF of clusters of different masses.

We determine the composite LF for early- and late-type galaxies, where the
typing is based on the galaxy u-r colors. The late-type LF is well fitted by a
single Schechter function with a steep slope (alpha=-2.0 in the r band, within
r200}). The early-type LF instead cannot be fitted by a single Schechter
function, and a composite of two Schechter functions is needed. The faint-end
upturn of the global cluster LF is due to the early-type cluster galaxies. The
shape of the bright-end tail of the early-type LF does not seem to depend upon
the local galaxy density or the distance from the cluster center. The late-type
LF shows a significant variation only very near the cluster center. On the
other hand, the faint-end tail of the early-type LF shows a significant and
continuous variation with the environment. We provide evidence that the process
responsible for creating the excess population of dwarf early type galaxies in
clusters is a threshold process that occurs when the density exceeds ~500 times
the critical density of the Universe. We interpret our results in the context
of the ‘harassment’ scenario, where faint early-type cluster galaxies are
predicted to be the descendants of tidally-stripped late-type galaxies.

References and citations for this submission:

SLAC-SPIRES HEP (refers to ,
cited by, arXiv reformatted)

Which authors of this paper are endorsers?