  Black holes formed in the early universe, prior to the formation of stars,
can exist as dark matter and also contribute to the black hole merger events
observed in gravitational waves. We set a new limit on the abundance of
primordial black holes (PBHs) by considering interactions of PBHs with the
interstellar medium, which result in the heating of gas. We examine generic
heating mechanisms, including emission from the accretion disk, dynamical
friction, and disk outflows. Using the data from the Leo T dwarf galaxy, we set
a new cosmology-independent limit on the abundance of PBHs in the mass range
$\mathcal{O}(1) M_{\odot}-10^7 M_{\odot}$, relevant for the recently detected
gravitational wave signals from intermediate-mass BHs.
