Cross identification between X-ray and Optical Clusters of Galaxies in the SDSS DR7 Field
(1 vote over all institutions)
We use the ROSAT all sky survey X-ray cluster catalogs and the optical SDSS DR7 galaxy and group catalogs to cross-identify X-ray clusters with their optical counterparts, resulting in a sample of 201 X-ray clusters in the sky coverage of SDSS DR7(Appendix B). We investigate various correlations between the optical and X-ray properties of these X-ray clusters, and find that the following optical properties are correlated with the X-ray luminosity: the central galaxy luminosity ($\propto \Lx^{0.28}$), the central galaxy mass ($\propto \Lx^{0.31}$), the characteristic group luminosity ($\propto \Lx^{0.43}$), the group stellar mass ($\propto \Lx^{0.46}$), with typical 1-$\sigma$ scatter of $\sim 0.7$ in $\log \Lx$. We obtain an unbiased fundamental plane relation between the X-ray luminosity, the central galaxy stellar mass and the characteristic satellite stellar mass as ${\log L_X} = -4.894 + 2.108 \log (M_{\ast, c} + 0.506 M_{\rm sat})$ (and in terms of luminosities, as ${\log L_X} = -4.108 + 2.179 \log (L_c + 0.484 L_{\rm sat})$), with reduced scatter $\sim 0.42$ ($\sim 0.50$). We find that the halo masses estimated using the velocity dispersion of satellite galaxies are not very reliable, while those estimated using the ranking of characteristic group stellar mass or using the X-ray luminosity scaling relation are much more reliable, with scatter $\sim 0.25$ dex and $\sim 0.20$ dex respectively. Comparing the properties of the groups of similar mass and redshift that are X-ray luminous or under-luminous, we find that X-ray luminous groups, have more faint satellite galaxies and the red fraction in their satellite galaxies is also enhanced.
