The Impact of Galaxy Formation on the Sunyaev-Zeldovich 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 eleven 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 and 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 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 ~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, the comparison with recent observations of the SZE scaling relations highlights the importance of galaxy formation in theoretical modelling of clusters and shows that current generation of simulations produce clusters with gross properties quite similar to their observed counterparts.