Escalating core formation with dark matter self-heating
  Exothermic scatterings of dark matter (DM) produce DM particles with
significant kick velocities inside DM halos. In collaboration with DM
self-interaction, the excess kinetic energy of the produced DM particles is
distributed to the others, which self-heats the DM particles as a whole. The DM
self-heating is efficient towards the halo center, and the heat injection is
used to enhance the formation of a uniform density core inside halos. The
effect of DM self-heating is expected to be more significant in smaller halos
for two reasons: 1) the exothermic cross section times the relative velocity,
$\left\langle\sigma_{\rm exo}v_{\rm rel}\right\rangle$, is constant; 2) and the
ratio of the injected heat to the velocity dispersion squared gets larger
towards smaller halos. For the first time, we quantitatively investigate the
core formation from DM self-heating for halos in a wide mass range
($10^{9}$-$10^{15}\,{\rm M}_\odot$) using the gravothermal fluid formalism.
Notably, we demonstrate that the core formation is sharply escalating towards
smaller halos by taking the self-heating DM (i.e., DM that semi-annihilates and
self-interacts) as an example. We show that the sharp escalation of core
formation may cause a tension in simultaneously explaining the observed central
mass deficit of Milky Way satellites, and field dwarf/low surface brightness
spiral galaxies. While the details of the self-heating effect may differ among
models, we expect that the sharp halo-mass dependence of the core formation is
a general feature of exothermic DM.
