AAS 195th Meeting, January 2000
Session 120. Clusters of Galaxies and Their Contents
Oral, Saturday, January 15, 2000, 10:00-11:30am, Centennial III

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[120.03] Scaling Laws and the Mass Function of Galaxy Clusters and Groups

Donald Horner (UMD/GSFC)

Scaling laws between galaxy cluster properties, such as the x-ray luminosity-temperature relation (L-T) and the total mass-temperature relation (M-T), reflect the underlying physics in cluster formation and evolution. We derive the L-T relationship over several orders of magnitude in luminosity, from rich clusters to groups, for over 200 clusters observed with ASCA. We also present the results from one of the first studies of the M-T relationship using data drawn from the literature for a variety of mass estimators.

The mass function of galaxy clusters provides a direct test of cosmological theories of structure formation and strongly constrains the value of Omega0. However, estimates of the local MF have largely been based on optical samples, and the MF is poorly measured at the mass scale of groups. Large, flux-limited samples of galaxy clusters and groups are becoming available from searches based on ROSAT PSPC data. We the apply the L-T and M-T scaling laws to estimate the local mass function of clusters and groups. We compare with earlier MFs based on optical samples and with theoretical predictions of the MF.

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