A Critical Assessment of Solutions to the Galaxy Diversity Problem

TL;DR

This study compares different dark matter models, including SIDM and CDM with feedback, to explain the diversity in galaxy rotation curves, finding both models fit the data well without a clear preference for one.

Contribution

It provides a comprehensive comparison of SIDM and feedback-affected CDM models using a large galaxy dataset, addressing previous methodological issues.

Findings

Both SIDM and feedback-affected CDM models outperform no-feedback CDM in fitting rotation curves.

No strong statistical preference between SIDM and feedback-affected CDM models.

Models are consistent with standard cosmological relations.

Abstract

Galactic rotation curves exhibit a diverse range of inner slopes. Observational data indicates that explaining this diversity may require a mechanism that correlates a galaxy's surface brightness with the central-most region of its dark matter halo. In this work, we compare several concrete models that capture the relevant physics required to explain the galaxy diversity problem. We focus specifically on a Self-Interacting Dark Matter (SIDM) model with an isothermal core and two Cold Dark Matter (CDM) models with/without baryonic feedback. In contrast to the CDM case, the SIDM model can lead to the formation of an isothermal core in the halo, and is also mostly insensitive to baryonic feedback processes, which act on longer time-scales. Using rotation curves from 90 galaxies in the Spitzer Photometry and Accurate Rotation Curves (SPARC) catalog, we perform a comprehensive model comparison that addresses issues of statistical methodology from prior works. The best-fit halo models that we recover are consistent with standard CDM concentration-mass and abundance matching relations. We find that both the SIDM and feedback-affected CDM models are better than a CDM model with no feedback in explaining the rotation curves of low and high surface brightness galaxies in the sample. However, when compared to each other, there is no strong statistical preference for either the SIDM or the feedback-affected CDM halo model as the source of galaxy diversity in the SPARC catalog.