A constraint on light primordial black holes from the interstellar
  medium temperature
  Primordial black holes are a viable dark matter candidate. They decay via
Hawking evaporation. Energetic particles from the Hawking radiation interact
with interstellar gas, depositing their energy as heat and ionization. For a
sufficiently high Hawking temperature, fast electrons produced by black holes
deposit a substantial fraction of energy as heat through the Coulomb
interaction. Using the dwarf galaxy Leo T, we place an upper bound on the
fraction of primordial black hole dark matter. For $M < 5 \times 10^{-17}
M_\odot$, our bound is competitive with or stronger than other bounds.
