Stringent Constraints on Self-Interacting Dark Matter Using Milky-Way Satellite Galaxies Kinematics

Self-interacting dark matter (SIDM) has been proposed to address small-scale challenges faced by the cold dark matter (CDM) paradigm, such as the diverse density profiles observed in dwarf galaxies. In this study, we analyze the kinematics of dwarf galaxies by incorporating the effects of gravothermal core collapse into SIDM models using a semi-analytical subhalo framework. Our analysis covers the stellar kinematics of both classical and ultrafaint dwarf galaxies. The results indicate a bimodal preference for small and large self-interaction cross sections in ultrafaint dwarf galaxies, while in classical dwarfs, larger cross sections progressively decrease the model's statistical support. The combined analysis decisively prefers CDM to SIDM when the self-interaction cross section per unit mass, $\sigma/m$, exceeds $\sim$0.2 cm$^2$/g, if a velocity-independent cross section is assumed. Our study significantly enhances our understanding of dark matter dynamics on small scales.