Resolved H-alpha Maps of Star-forming Galaxies in Distant Clusters: Towards a Physical Model of Satellite Galaxy Quenching

It has been known for decades that satellite galaxies are always less star forming than central galaxies of similar mass. New, sophisticated modeling of satellites at both z = 0 and z = 1 has shown that the quenching of star formation in satellites must be a rapid process, occurring on a timescale of only ~ 0.5 Gyr. Despite good constraints on the quenching timescale, the detailed physics of how satellites actually shut down their star formation is still heavily debated. What is now desperately needed are high-quality observations of satellite galaxies directly in the process of quenching. In particular, resolved H-alpha maps would be extremely informative because H-alpha is a near instantaneous measure of the current SFR, showing where and when star formation is quenched. Thus far, these maps are only available locally for satellite galaxies in the Virgo cluster; however, they are fascinating. In H-alpha emission Virgo satellites are completely different than central galaxies, with >50% having highly truncated and disturbed disks, suggesting an outside-in truncation of star formation. We propose to obtain the first resolved H-alpha maps of star-forming satellite galaxies in massive clusters at z ~ 1. This high-redshift data will be critical to determine how satellite quenching evolves over time, as satellites have much higher gas fractions and star formation rates at z ~ 1. We will compare the H-alpha luminosities, sizes and profiles of the satellites to central galaxies in the 3D-HST survey and quantify how quenching affects star-forming disks at z ~ 1. This information will be key input for the next generation of physical models of satellite quenching.