A homogeneous measurement of the delay between the onsets of gas stripping and star formation quenching in satellite galaxies of groups and clusters

We combine orbital information from N-body simulations with an analytic model for star formation quenching and SDSS observations of galaxy positions, redshifts, and colours to infer the differential effect of the group/cluster environment on star formation in satellite galaxies. We repeat a similar exercise with a similar model for gas stripping and supplement the same input catalogue with HI fluxes from the ALFALFA survey. The statistical models are motivated by and tested on the Hydrangea cosmological hydrodynamical simulation suite. Our models recover the typical time when galaxies in the satellite population are stripped and quenched: stripping in massive ($M_{\rm vir}\sim 10^{14.5}\,{\rm M}_\odot$) clusters typically occurs at or just before the first pericentric passage, and up to $\sim 4\,{\rm Gyr}$ later in low mass ($\sim 10^{12.5}\,{\rm M}_\odot$) groups. Quenching occurs later: Balmer emission lines typically fade $\sim 4\,{\rm Gyr}$ ($6.5\,{\rm Gyr}$) after first pericentre in clusters (groups), followed a few hundred ${\rm Myr}$ later by reddening in $(g-r)$ colour. These 'delay timescales' are remarkably constant across the entire satellite stellar mass range probed ($\sim 10^{9.5}$--$10^{11}\,{\rm M}_\odot$); this feature is closely tied to our treatment of 'group pre-processing'. While our measurements are qualitatively consistent with the `delayed-then-rapid' quenching scenario advocated for by several other studies, we find significantly longer delay times. The origin of this apparent discrepancy is difficult to pinpoint. However, our unique use of a homogeneous analysis and input catalogues yields new insight into the sequence of events leading to quenching across wide intervals in host and satellite mass.