Revealing black holes with Gaia

TL;DR

This paper predicts that Gaia will discover thousands of black hole systems with luminous companions in the Milky Way, providing new insights into black hole formation and properties through astrometric observations.

Contribution

It presents a comprehensive population synthesis model estimating Gaia's potential to detect black hole binaries with luminous companions, incorporating detailed stellar and binary evolution physics.

Findings

Gaia could discover 3,800 to 12,000 BH-LCs.

Distributions of eccentricities and masses can constrain black hole natal kicks.

Gaia-detected BH-LCs have distinct orbital properties from other detection methods.

Abstract

We estimate the population of black holes with luminous stellar companions (BH-LCs) in the Milky Way (MW) observable by Gaia. We evolve a realistic distribution of BH-LC progenitors from zero-age to the current epoch taking into account relevant physics, including binary stellar evolution, BH-formation physics, and star formation rate, to estimate the BH-LC population in the MW today. We predict that Gaia will discover between 3800 and 12,000 BH-LCs by the end of its 5 yr mission, depending on BH natal kick strength and observability constraints. We find that the overall yield, and distributions of eccentricities and masses of observed BH-LCs can provide important constraints on the strength of BH natal kicks. Gaia-detected BH-LCs are expected to have very different orbital properties compared to those detectable via radio, X-ray, or gravitational wave observations.