Work

An enhanced isothermal jeans approach to constraining dark matter self-interactions from galactic kinematics

Year: 2026

Type: article

Abstract: ABSTRACT We present an improved semi-analytical model to predict density profiles of self-interacting dark matter (SIDM) haloes and apply it to constrain the self-scattering cross-section using SPARC (Spitzer Photometry and Accurate Rotation Curves) galaxy rotation curves. Building on the isothermal Jeans approach, our model incorporates (i) velocity-dependent cross-sections, (ii) an empirical treatment of core collapse, and (iii) enhanced robustness for identifying solutions. These advances allow us to fit a large sample of galaxies, including systems with baryon-dominated centres often excluded in earlier studies. We find that roughly 1/6 of galaxies admit both a core-growth and a core-collapse solution, while the rest favour a unique evolutionary state. Joint constraints across the sample reveal clear velocity dependence: the allowed parameter space forms an L-shaped degeneracy, where both nearly constant, low cross-sections ($\sigma _0\sim 2\,$cm$^2$ g−1 and $\omega \gtrsim 500\,$km s−1) and strongly velocity-dependent models ($\sigma _0\sim 100\,$cm$^2$ g−1 and $\omega \sim 60\,$km s−1) are viable. Adopting the core-growth interpretation yields best-fitting values $\sigma _0\simeq 5\,$cm$^2$ g−1 and $\omega \simeq 250\,$km s−1. Our constraints are remarkably consistent with previous results derived from a variety of independent probes. Compared to cold dark matter (CDM) models, SIDM outperforms simple adiabatic-contraction profiles and rivals empirical feedback-based CDM profiles, yet shows no correlation with stellar-to-halo mass ratio, a proxy for feedback strength, offering a distinct explanation for dwarf galaxy diversity. Moreover, SIDM does not affect galaxy–halo scaling relations significantly and makes concentration systematically lower. Our results highlight SIDM as a compelling framework for small-scale structure, while future low-mass kinematic data will be crucial for breaking degeneracies in velocity-dependent cross-section models.

Source: Monthly Notices of the Royal Astronomical Society

DOI: 10.1093/mnras/stag969

Authors: Zixiang Jia, Fangzhou Jiang, Shubo Li, Ran Li, Jing Wang, Ling Zhu