  When dark matter halos are accreted by massive host clusters, strong
gravitational tidal forces begin stripping mass from the accreted subhalos.
This stripping eventually removes all mass beyond a subhalo's tidal radius, but
the unbound mass remains in the vicinity of the satellite for at least a
dynamical time t_dyn. The N-body subhalo study of Chamberlain et al. verified
this picture and pointed out a useful observational consequence: measurements
of subhalo correlations beyond the tidal radius are sensitive to the infall
time, t_infall, of the subhalo onto its host. We perform this cross-correlation
measurement using ~ 160,000 red satellite galaxies in SDSS redMaPPer clusters
and find evidence that subhalo correlations do persist well beyond the tidal
radius, suggesting that many of the observed satellites fell into their current
host less than a dynamical time ago, t_infall < t_dyn. Combined with estimated
dynamical times t_dyn ~ 3-5 Gyr and SED fitting results for the time at which
satellites stopped forming stars, t_quench ~ 6 Gyr, we infer that for a
significant fraction of the satellites, star formation quenched before those
satellites entered their current hosts. The result holds for red satellites
over a large range of cluster-centric distances 0.1 - 0.6 Mpc/h. We discuss the
implications of this result for models of galaxy formation.

Astrophysics of Galaxies;Cosmology and Nongalactic Astrophysics