First measurement of the characteristic depletion radius of dark matter haloes from weak lensing

TL;DR

This study presents the first observational measurement of the characteristic depletion radius of dark matter haloes using weak lensing data, revealing its relation to virial and splashback radii and its approximate universality.

Contribution

It introduces the first measurement of the depletion radius from weak lensing and compares it with theoretical predictions, expanding understanding of halo boundary definitions.

Findings

Depletion radius is about 2.5 times the virial radius.

Depletion radius is roughly 1.7 to 3 times the splashback radius.

Enclosed density within depletion radius is approximately 29 times the mean matter density.

Abstract

We use weak lensing observations to make the first measurement of the characteristic depletion radius, one of the three radii that characterize the region where matter is being depleted by growing haloes. The lenses are taken from the halo catalog produced by the extended halo-based group/cluster finder applied to DESI Legacy Imaging Surveys DR9, while the sources are extracted from the DECaLS DR8 imaging data with the Fourier_Quad pipeline. We study halo masses $12 < \log ( M_{\rm grp} ~[{\rm M_{\odot}}/h] ) \leq 15.3$ within redshifts $0.2 \leq z \leq 0.3$. The virial and splashback radii are also measured and used to test the original findings on the depletion region. When binning haloes by mass, we find consistency between most of our measurements and predictions from the CosmicGrowth simulation, with exceptions to the lowest mass bins. The characteristic depletion radius is found to be roughly $2.5$ times the virial radius and $1.7 - 3$ times the splashback radius, in line with an approximately universal outer density profile, and the average enclosed density within the characteristic depletion radius is found to be roughly $29$ times the mean matter density of the Universe in our sample. When binning haloes by both mass and a proxy for halo concentration, we do not detect a significant variation of the depletion radius with concentration, on which the simulation prediction is also sensitive to the choice of concentration proxy. We also confirm that the measured splashback radius varies with concentration differently from simulation predictions.