We present a per centlevel accurate model of the lineofsight velocity distribution of galaxies around dark matter haloes as a function of projected radius and halo mass. The model is developed and tested using synthetic galaxy catalogues generated with the UniverseMachine run on the MultiDark Planck 2 Nbody simulations. The model decomposes the galaxies around a cluster into three kinematically distinct classes: orbiting, infalling, and interloping galaxies. We demonstrate that: (1) we can statistically distinguish between these three types of galaxies using only projected lineofsight velocity information; (2) the halo edge radius inferred from the lineofsight velocity dispersion is an excellent proxy for the threedimensional halo edge radius; and (3) we can accurately recover the full velocity dispersion profile for each of the three populations of galaxies. Importantly, the velocity dispersion profiles of the orbiting and infalling galaxies contain five independent parameters – three distinct radial scales and two velocity dispersion amplitudes – each of which is correlated with mass. Thus, the velocity dispersion profile of galaxy clusters has inherent redundancies that allow us to perform nontrivial systematics checks from a single data set. We discuss several potential applications of our new model for detecting the edge radius and constraining cosmology and more »
 Publication Date:
 NSFPAR ID:
 10403679
 Journal Name:
 Monthly Notices of the Royal Astronomical Society
 Volume:
 521
 Issue:
 3
 Page Range or eLocationID:
 p. 39813990
 ISSN:
 00358711
 Publisher:
 Oxford University Press
 Sponsoring Org:
 National Science Foundation
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