Constraints on primordial black holes from observation of stars in dwarf galaxies

Abstract

We propose a way to constrain the primordial black hole (PBH) abundance in the range of PBH masses $m$ around $10^{20}$g based on their capture by Sun-like stars in dwarf galaxies, with subsequent star destruction. We calculate numerically the probability of a PBH capture by a star at the time of its formation in an environment typical of dwarf galaxies. Requiring that no more than a fraction $\xi$ of stars in a dwarf galaxy is destroyed by PBHs translates into an upper limit on the PBH abundance. For the parameters of Triangulum II and $\xi=0.5$, we find that no more than $\sim 35\%$ of dark matter can consist of PBHs in the mass range $10^{18} - \text{(a few)}\times 10^{21}$g. The constraints depend strongly on the parameter $\xi$ and may significantly improve if smaller values of $\xi$ are established from observations. An accurate determination of $\xi$ from dwarf galaxy modeling is thus of major importance.