On the Cluster Physics of Sunyaev-Zel'dovich Surveys I: The Influence of
  Feedback, Non-thermal Pressure and Cluster Shapes on Y-M Scaling Relations
  The utility of large Sunyaev Zel'dovich (SZ) surveys for determining
cosmological parameters from cluster abundances is limited by the theoretical
uncertainties in the integrated SZ-flux-to-mass relation, Y-M. We explore how
non-thermal pressure and the anisotropic shape of the gas distribution of the
intracluster medium (ICM) impacts Y-M scaling using a suite of SPH simulations
of the cosmic web. We contrast results for models with different treatments of
entropy injection and transport, varying radiative cooling, star formation and
accompanying supernova feedback, cosmic rays, and energetic feedback from
active galactic nuclei (AGN). We find that the gas kinetic-to-thermal pressure
ratio from internal bulk motions depends on the cluster mass, and increases in
the outer-cluster due to enhanced substructure, as does the asphericity of the
ICM gas. With only a ~5-10% correction to projected (observable) ellipticities,
we can infer the 3D ellipticities. Our simulated Y-M-slope roughly follows the
self-similar prediction, except for a steepening due to a deficit of gas in
lower mass clusters at low redshift in our AGN-feedback simulations. AGN
feedback enhances slightly the overall Y-M-scatter, from ~11% to ~13%, a
reflection of accretion history variations due to cluster merging. If we split
the cluster system into lower, middle and upper bands of both P_kin/P_th and
long-to-short axis ratio, we find a ~10% effect on Y-M. Identifying observable
second parameters related to internal bulk flows and anisotropy for
cluster-selection to minimize Y-M scatter in a "fundamental plane" would allow
tighter cosmological parameter constraints.
