Collisional Baryon-Dominated Dwarf Galaxies: A New Probe of Bursty Feedback and Dark Matter Physics

Abstract: High-velocity collisions between gas-rich ultra-diffuse galaxies present a promising formation channel for baryon-dominated dwarf galaxies (BDDGs). Using hydrodynamical simulations, we show that the progenitors' baryonic binding energy, $|E_{\rm bind}|$, critically controls the outcome. Repeated potential fluctuations, e.g., from bursty feedback, inject energy and reduce $|E_{\rm bind}|$ by $\approx 15\%$, yielding fewer but substantially more massive BDDGs. By contrast, elastic self-interacting dark matter produces comparable cores without lowering $|E_{\rm bind}|$, resulting in negligible effect. This provides a novel way to distinguish between two leading galactic core formation channels, i.e., the baryon feedback and elastic dark matter self-interaction. Among 15 paired simulation runs, 13 show higher BDDG masses in the weakened-binding case, and about two thirds exhibit $>100\%$ mass enhancements. The simulations also predict systematically lower gas fractions due to sustained post-collision star formation, yielding a clean observational signature. Upcoming wide-field imaging (CSST, LSST), HI surveys (FAST), and kinematic follow-up will be crucial to test this scenario.