RASS-SDSS galaxy cluster survey
II. A unified picture of the cluster luminosity function
Max-Planck-Institut fur extraterrestrische Physik, 85748 Garching, Germany e-mail: email@example.com
2 European Southern Observatorty, Karl Scharzschildstr. 2, 85748 Garching b. München, Germany
Accepted: 1 December 2004
We constructed the composite luminosity function (LF) of clusters of galaxies in the five SDSS photometric bands u, g, r, i and z from the RASS-SDSS galaxy cluster catalog. Background and foreground galaxies are subtracted using both a local and a global background correction to take in account the presence of large scale structures and field to field variations, respectively. The composite LF clearly shows two components: a bright-end LF with a classical slope of –1.25 in each photometric band, and a steeper faint-end LF () in the dwarf galaxy region. The observed upturn of the faint galaxies has a location ranging from in the g band to in the z band. To study the universality of the cluster LF we compare the individual cluster LFs with the composite luminosity function. In agreement with the composite LF, a single Schechter component is not a good fit for the majority of the clusters. We fit a Schechter function to the bright-end of the individual cluster LFs in the magnitude region brighter than the observed upturn of the dwarf galaxies. The bright-end of the galaxy clusters shows the same shape in all the systems. To study the behavior of the individual faint-end LF we define the Dwarf to Giant galaxy Ratio (DGR) of the single clusters. The distribution of DGR has a spread much larger than the statistical errors. The DGR clearly anti-correlates with both X-ray and optical cluster luminosities. This anti-correlation is most likely due to the choice of a fixed metric aperture for all the clusters. Therefore, because of this effect, the different cluster physical sizes must be taken into account before comparing the LF of different clusters.
Key words: galaxies: clusters: general / galaxies: general
© ESO, 2005