RASS-SDSS Galaxy cluster survey. IV. A ubiquitous dwarf galaxy population in clusters

Details RASS-SDSS Galaxy cluster survey. IV. A ubiquitous dwarf galaxy population in clusters RASS-SDSS Galaxy cluster survey. IV. A ubiquitous dwarf galaxy population in clusters

Jan 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006a%26a...445...29p&link_type=abstract

Astronomy and Astrophysics, Volume 445, Issue 1, January I 2006, pp.29-42

Astronomy and Astrophysics

Astrophysics

53

Galaxies: Clusters: General, Galaxies: Luminosity Function, Mass Function

Scientific paper

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 (α=-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.

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