Simulating the "hidden giant" in cold and self-interacting dark matter models

TL;DR

This study uses N-body simulations to explore how the Antlia 2 galaxy can be formed in cold and self-interacting dark matter models, revealing conditions under which such galaxies can exist and their observable properties.

Contribution

The paper provides the first detailed simulation-based analysis of Antlia 2 formation in both CDM and SIDM scenarios, highlighting the effects of halo concentration and self-interactions.

Findings

Antlia 2-like galaxies can form in CDM with low halo concentration and diffuse stellar distributions.

SIDM models relax the conditions needed for Antlia 2 formation.

Simulated galaxies show similar stellar velocity dispersions after tidal evolution.

Abstract

We perform a series of controlled N-body simulations to study realizations of the recently discovered Antlia 2 galaxy in cold dark matter (CDM) and self-interacting dark matter (SIDM) scenarios. Our simulations contain six benchmark models, where we vary the initial halo concentration and the self-scattering cross section. We adopt well-motivated initial stellar and halo masses, and our fiducial orbit has a small pericenter. After evolving in the Milky Way's tidal field, the simulated galaxies experience significant mass loss and their stellar distributions expand accordingly. These tidal effects are more prominent if the initial halo concentration is lower and if the self-scattering cross section is larger. Our results show that Antlia 2-like galaxies could be realized in CDM if the halo concentration is low and the stellar distribution is diffuse at the infall time, while these conditions could be relaxed in SIDM. We also find all the simulated galaxies predict approximately the same stellar velocity dispersion after imposing selection criteria for stellar particles. This has important implications for testing dark matter models using tidally disturbed systems.