Constraining the Coexistence of Freeze-in Dark Matter and Primordial Black Holes

Particle dark matter and primordial black holes (PBH) might
coexist with appreciable cosmic abundances, with both contributing to the
observed dark matter density $Omega_{rm DM}$. Large populations of PBH
(with $Omega_{rm PBH}sim Omega_{rm DM}$) are tightly constrained for
PBH heavier than $10^{-11} M_odot$. However, large fractional abundances
with  $ f_{rm PBH}simeq Omega_{rm PBH}/Omega_{rm DM}sim0.01$ are
consistent with the limits on PBH for a wide range of PBH masses.
Scenarios with significant populations of both particle dark matter and
PBH are intriguing. Notably, if the particle dark matter has interactions
with the Standard Model, new constraints arise due to pair-annihilations
that are enhanced by the PBHs, resulting in dark matter indirect detection
constraints on $f_{rm PBH}$. Here we derive the bounds on mixed scenarios
in which PBHs coexist with particle dark matter whose relic abundance is
set via freeze-in  (``FIMPs''). We show that while the restrictions on
$f_{rm PBH}$  are less constraining for FIMPs than WIMPs, modest bounds
still arise for large classes of models. We examine both IR and UV
freeze-in scenarios, including the case of ``super-heavy'' particle dark
matter with PeV scale mass.