Abstract

The Milky Way contains of order 100 million stellar-mass black holes. Yet, fewer than 100 black hole candidates are known in the Milky Way, and only about 25 are dynamically confirmed. Our view of the black hole population has been shaped almost entirely by observations of X-ray binaries and gravitational wave sources, both of which represent rare outcomes of binary evolution. I will discuss recent efforts to uncover the much larger population of Galactic black holes in non-interacting binaries, focusing particularly on astrometry from the Gaia mission. Compared to previous surveys, Gaia is revealing post-interaction binaries in wider orbits, whose properties are difficult to explain with standard binary evolution models. I will discuss how the Gaia catalogs can be leveraged for statistical inference, despite their complex selection function, and how they can discriminate between competing formation models.