BOSS galaxies in X-ray clusters

The HOD of BOSS low-redshift (LOWZ: 0.2<z<0.4) and Constant-Mass (CMASS: 0.43<z<0.7) galaxies is inferred via their association with the dark-matter halos of 174 X-ray-selected galaxy clusters drawn from the XMM Cluster Survey (XCS).

Halo masses are determined for each galaxy cluster based on X-ray temperature measurements, and range between log_10_(M_180_/M_{sun}_)=13-15. Our directly measured HODs are consistent with the HOD-model fits inferred via the galaxy-clustering analyses of Parejko et al. for the BOSS LOWZ sample and White et al. for the BOSS CMASS sample. Under the simplifying assumption that the other parameters that describe the HOD hold the values measured by these authors, we have determined a best-fit alpha-index of 0.91+/-0.08 and 1.27^+0.03^_-0.04_ for the CMASS and LOWZ HOD, respectively.