The impact of galaxy formation on the Sunyaev-Zel'dovich effect of galaxy clusters

We study the effects of galaxy formation on the Sunyaev-Zel'dovich effect (SZE) observable-mass relations using high-resolution cosmological simulations. The simulations of 11 individual clusters spanning a decade in mass are performed with the shock-capturing Eulerian adaptive mesh refinement N-body+gasdynamics ART code. To assess the impact of galaxy formation, we compare two sets of simulations performed in an adiabatic regime ( without galaxy formation) with those with several physical processes critical to various aspects of galaxy formation: radiative cooling, star formation, stellar feedback, and metal enrichment. We show that a SZE signal integrated to a sufficiently large fraction of cluster volume correlates strongly with its enclosed mass, independent of details of gas physics and the dynamical state of the cluster. The slope and redshift evolution of the SZE flux-mass relation are also insensitive to processes of galaxy formation and are well characterized by a simple self-similar cluster model. Its normalization, on the other hand, is significantly affected by gas cooling and associated star formation. Our simulations show that inclusion of these processes suppresses the normalization by approximate to 30%-40%. The effect is due to a decrease in gas mass fraction, which is offset slightly by an increase in gas-mass-weighted temperature. Gas cooling and star formation also cause an increase in total mass and modify the normalization by a few percent. Finally, we compare the results of our simulations to recent observations of the SZE scaling relations obtained using 36 OVRO/BIMA SZE + Chandra X-ray observations. The comparison highlights the importance of galaxy formation in theoretical modeling of clusters and shows that the current generation of simulations produces clusters with gross properties quite similar to their observed counterparts.