  We present the mass-X-ray observable scaling relationships for clusters of
galaxies using the XMM-Newton cluster catalog of Snowden et al. Our results are
roughly consistent with previous observational and theoretical work, with one
major exception. We find 2-3 times the scatter around the best fit mass scaling
relationships as expected from cluster simulations or seen in other
observational studies. We suggest that this is a consequence of using
hydrostatic mass, as opposed to virial mass, and is due to the explicit
dependence of the hydrostatic mass on the gradients of the temperature and gas
density profiles. We find a larger range of slope in the cluster temperature
profiles at r_{500} than previous observational studies. Additionally, we find
only a weak dependence of the gas mass fraction on cluster mass, consistent
with a constant. Our average gas mass fraction results argue for a closer study
of the systematic errors due to instrumental calibration and analysis method
variations. We suggest that a more careful study of the differences between
various observational results and with cluster simulations is needed to
understand sources of bias and scatter in cosmological studies of galaxy
clusters.
