Scaling relations for dark matter core density and radius from Chandra X-ray cluster sample

TL;DR

This study investigates the relationship between dark matter core density and radius in galaxy clusters, finding a near-inverse proportionality and minimal deviation from a constant surface density, refining previous cluster analyses.

Contribution

It provides the first systematic analysis of dark matter surface density scaling in galaxy clusters, incorporating gas and star mass effects, and confirms a near-inverse relation between core density and radius.

Findings

Dark matter core density scales approximately as r_c^{-1.08}

Surface density deviations are only about 1.4 sigma from constancy

Intrinsic scatter in the relation is about 18%

Abstract

A large number of studies have found that the dark matter surface density, given by the product of the dark matter core radius ($r_c$) and core density ($\rho_c$) is approximately constant for a wide range of galaxy systems. However, there has been only one systematic study of this {\it ansatz} for galaxy clusters by Chan (arXiv:1403.4352), who found that the surface density for clusters is not constant and $\rho_c \sim r_c^{-1.46}$. We carry out this test for an X-ray sample of 12 relaxed clusters from Chandra observations, implementing the same procedure as Chan, but also accounting for the gas and star mass. We find that $\rho_c \propto r_c^{-1.08 \pm 0.055}$, with an intrinsic scatter of about 18%. Therefore, the dark matter surface density for our cluster data shows deviations from a constant value at only about 1.4$\sigma$.