Constraining the Nature of Dark Matter from Tidal Radii of Cluster Galaxy Subhalos

TL;DR

This study uses gravitational lensing data from galaxy clusters to compare the properties of subhalos with predictions from cold dark matter and self-interacting dark matter models, aiming to constrain the nature of dark matter.

Contribution

It provides observational constraints on dark matter models by analyzing subhalo truncation radii in multiple galaxy clusters, testing SIDM versus CDM predictions.

Findings

Subhalo outer extents are consistent with CDM predictions.

Results support collisionless cold dark matter over self-interacting models.

Tidal radii serve as a diagnostic for dark matter properties.

Abstract

Gravitational lensing by galaxy clusters provides a powerful probe of the spatial distribution of dark matter and its microphysical properties. Strong and weak lensing constraints on the density profiles of subhalos and their truncation radii offer key diagnostics for distinguishing between collisionless cold dark matter (CDM) and self-interacting dark matter (SIDM). Notably, in the strongly collisional SIDM regime, subhalo core collapse and enhanced mass loss from ram-pressure stripping predict steeper central density slopes and more compact truncation radii--features that are directly testable with current lensing data. We analyze subhalo truncation in eight lensing clusters (Abell 2218, 383, 963, 209, 2390, and MACS J0416.1, J1206.2, J1149.6) that span the redshift range <$z_\text{spec}$>$ \simeq 0.17$-$0.54$ with virial masses $M_{200} \simeq0.41$-$2.2\times 10^{15}$ M$_\odot$ to constrain SIDM versus CDM. Our results indicate that the outer spatial extents of subhalos are statistically consistent with CDM, corroborated by redshift- and mass-matched analogs from the Illustris-TNG simulations. We conclude that the tidal radii of cluster galaxy subhalos serve as an important and complementary diagnostic of the nature of dark matter in these violent, dense environments.