Cusp-to-Core Transition of Dark Matter Halos across Galaxy Mass Scales

TL;DR

This study analyzes dark matter density profiles across galaxy mass scales, revealing a transition from cuspy to core-like structures likely influenced by baryonic feedback, with implications for understanding galaxy formation.

Contribution

It provides empirical evidence of a cusp-to-core transition in dark matter halos across different galaxy masses, highlighting the role of baryonic feedback in shaping inner dark matter structures.

Findings

Diversity in inner density slopes of galaxies from cuspy to core-like.

Many galaxies deviate from cold dark matter predictions, showing shallower cores.

Lower-mass dwarfs and galaxy clusters tend to follow cuspy profiles.

Abstract

We investigate the diversity of dark matter (DM) density profiles in a large sample of late-type galaxies from the SPARC database, with the goal of testing whether a cusp-to-core transition occurs across galaxy mass scales. We perform Bayesian fits to high-quality rotation curves using flexible halo models that allow for variations in the inner slopes of DM density profiles. We quantify the central dark matter structure using the surface density within the inner region of the halo, defined as $\Sigma_{\rm DM}(<0.01r_{V_{\rm max}})$, and compare the SPARC galaxies with Milky Way dwarf satellites as well as galaxy groups and clusters. Our results reveal significant diversity in the inner density slopes of SPARC galaxies, ranging from steep cusps to shallow cores, and show that many of them lie below the cuspy profiles predicted by the cold dark matter model, consistent with core-like structures. In contrast, both lower-mass dwarf galaxies and higher-mass galaxy clusters tend to follow the cuspy DM halos. These findings suggest that baryonic feedback may induce a cusp-to-core transition in Milky Way-mass galaxies, as predicted by hydrodynamical simulations. However, observational limitations and modeling uncertainties still prevent a definitive conclusion. This study provides new empirical insights into the halo mass-dependent nature of DM inner structures and the role of baryonic processes in shaping them.