Ram Pressure Stripping in Groups: Comparing Theory and Observations

Abstract

Ram pressure stripping may be the dominant mechanisms driving the evolution of galaxy colors in groups and clusters. In this paper, an analytic model of ram pressure stripping is confronted with observations of galaxy colors and star formation rates in groups using a group catalog drawn from the Sloan Digital Sky Survey. An observed increase in the fraction of galaxies residing on the red sequence, the red fraction, with both increasing group mass, $M_{gr}$, and decreasing satellite luminosity, $L_{sat}$, is predicted by the model. The size of the differences in the red fraction can be understood in terms of the effect of the scatter in satellite and cluster morphologies and satellite orbits on the relationship between $M_{gr}$ and $L_{sat}$ and the stripped gas fraction. Observations of the group galaxies' H$\delta$ and 4000\AA break spectral measures and a comparison of the distribution of $SFR/M_{\ast}$ for star forming galaxies in the groups and in isolation both indicate that the color differences observed in the groups are the result of slowly declining SFRs, as expected if the color change is driven by stripping of the outer H \textsc{i} disk.