THE X-RAY LUMINOSITY FUNCTION AND GAS MASS FUNCTION FOR OPTICALLY SELECTED POOR AND RICH CLUSTERS OF GALAXIES

摘要

We present the first X-ray luminosity function (XLF) for an optically selected sample of 49 nearby poor clusters of galaxies and a sample of 67 Abell clusters with z ≤ 0.15. We have extended the measured cluster XLF by more than a factor of 10 in X-ray luminosity. Our poor cluster sample was drawn from an optical catalog of groups with 0.01 ≤ z ≤ 0.03 composed of Zwicky galaxies. The X-ray emission was measured from the ROSAT all-sky survey. About 45% of the poor clusters were detected, with 0.5-2.0 keV luminosities from 1.7 to 65 X 10~(41) h~(-2) ergs s~(-1). These are among the X-ray brightest, optically selected poor clusters in the northern hemisphere. For this sample, the poor cluster XLF was found to be a smooth extrapolation of the rich cluster XLF. A new Hydro/N-body simulation of a hot + cold dark matter model with Ω_(total) = 1, Ω_ν = 0.2, and a baryon fraction of 7.5% was used to model and understand our observational selection effects. We found that the observed cluster gas mass function was consistent with our model.