The mass and galaxy distribution around SZ-selected clusters
  We present measurements of the radial profiles of the mass and galaxy number
density around Sunyaev-Zel'dovich-selected clusters using both weak lensing and
galaxy counts. The clusters are selected from the Atacama Cosmology Telescope
Data Release 5 and the galaxies from the Dark Energy Survey Year 3 dataset.
With signal-to-noise of 62 (43) for galaxy (weak lensing) profiles over scales
of about $0.2-20h^{-1}$ Mpc, these are the highest precision measurements for
SZ-selected clusters to date. Because SZ selection closely approximates mass
selection, these measurements enable several tests of theoretical models of the
mass and light distribution around clusters. Our main findings are: 1. The
splashback feature is detected at a consistent location in both the mass and
galaxy profiles and its location is consistent with predictions of cold dark
matter N-body simulations. 2. The full mass profile is also consistent with the
simulations; hence it can constrain alternative dark matter models that modify
the mass distribution of clusters. 3. The shapes of the galaxy and lensing
profiles are remarkably similar for our sample over the entire range of scales,
from well inside the cluster halo to the quasilinear regime. This can be used
to constrain processes such as quenching and tidal disruption that alter the
galaxy distribution inside the halo, and scale-dependent features in the
transition regime outside the halo. We measure the dependence of the profile
shapes on the galaxy sample, redshift and cluster mass. We extend the Diemer \&
Kravtsov model for the cluster profiles to the linear regime using perturbation
theory and show that it provides a good match to the measured profiles. We also
compare the measured profiles to predictions of the standard halo model and
simulations that include hydrodynamics. Applications of these results to
cluster mass estimation and cosmology are discussed.
