Year: 2015
Type: article
Abstract: The boundaries of cold dark matter halos are commonly defined to enclose a density contrast Δ relative to a reference (mean or critical) density. We argue that a more physical halo boundary choice is the radius at which accreted matter reaches its first orbital apocenter after turnaround. This splashback radius , , manifests itself as a sharp density drop in the halo outskirts, at a location that depends upon the mass accretion rate. We present calibrations of and the enclosed mass, , as a function of mass accretion rate and peak height. We find that is in the range for rapidly accreting halos and is for slowly accreting halos. Thus, halos and their environmental effects can extend well beyond the conventionally defined "virial" radius. We show that and evolve relatively strongly compared to other commonly used definitions. In particular, evolves significantly even for the smallest dwarf-sized halos at z = 0. We also contrast with the mass enclosed within four scale radii of the halo density profile, , which characterizes the inner halo. During the early stages of halo assembly, and evolve similarly, but in the late stages stops increasing while continues to grow significantly. This illustrates that halos at low z can have "quiet" interiors while continuing to accrete mass in their outskirts. We discuss potential observational estimates of the splashback radius and show that it may already have been detected in galaxy clusters.
Source: The Astrophysical Journal
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, National Aeronautics and Space Administration, Aspen Center for Physics, Johns Hopkins University, Ministry of Education, Culture, Sports, Science and Technology, Council for Science and Technology Policy, Kavli Institute for Cosmological Physics, University of Chicago, Japan Society for the Promotion of Science
Awards: G1432780348, G4357913612, Programs on Critical Problems in Physics, Astrophysics and Biophysics at the Aspen Center for Physics, Physics Frontier Center at the Kavli Institute for Cosmological Physics: Pushing Cosmology to the Edge, The Physics Frontier Center of the Kavli Institute for Cosmological Physics, Systematic study of the stellar initial mass function and its variation, G8896167186
OpenAlex ID: W1857637982