The impact of galaxy selection on the splashback boundaries of galaxy
  clusters
  We explore how the splashback radius ($R_{\rm sp}$) of galaxy clusters,
measured using the number density of the subhalo population, changes based on
various selection criteria using the IllustrisTNG cosmological galaxy formation
simulation. We identify $R_{\rm sp}$ by extracting the steepest radial gradient
in a stacked set of clusters in 0.5 dex wide mass bins, with our clusters
having halo masses $10^{13} \leq M_{\rm 200, mean} / {\rm M}_\odot \leq
10^{15}$. We apply cuts in subhalo mass, galaxy stellar mass, $i$-band absolute
magnitude and specific star formation rate. We find that, generally, galaxies
of increasing mass and luminosity trace smaller measured splashback radii
relative to the intrinsic dark matter radius. We also show that quenched
galaxies may be used to reliably reconstruct the dark matter splashback radius.
This trend is likely due to changes in the galaxy population. Additionally, we
are able to reconcile different observational predictions that $R_{\rm sp}$
based upon galaxy number counts and dark matter may either align or show
significant offset (e.g. those using optically- or SZ-selected clusters)
through the selection functions that these studies employ. Finally, we
demonstrate that changes in $R_{\rm sp}$ measured through number counts are not
due to a simple change in galaxy abundance inside and outside of the cluster.
