Synthetic catalog of black holes in the Milky Way^⋆

¹ Astronomical Observatory, Warsaw University Ujazdowskie 4, 00-478 Warsaw, Poland
e-mail: a.olejak@student.uw.edu.pl
² Center for Theoretical Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland
³ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
⁴ Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138, USA

Received: 23 August 2019
Accepted: 7 April 2020

Abstract

Aims. We present an open-access database that includes a synthetic catalog of black holes (BHs) in the Milky Way, divided by the components disk, bulge, and halo.

Methods. To calculate the evolution of single and binary stars, we used the updated population synthesis code StarTrack. We applied a new model of the star formation history and chemical evolution of Galactic disk, bulge, and halo that was synthesized from observational and theoretical data. This model can be easily employed for other studies of population evolution.

Results. We find that at the current Milky Way (disk+bulge+halo) contains about 1.2 × 10⁸ single BHs with an average mass of about 14 M_⊙, and 9.3 × 10⁶ BHs in binary systems with an average mass of 19 M_⊙. We present basic statistical properties of the BH population in three Galactic components such as the distributions of BH masses, velocities, or the numbers of BH binary systems in different evolutionary configurations.

Conclusions. The metallicity of a stellar population has a significant effect on the final BH mass through the stellar winds. The most massive single BH in our simulation of 113 M_⊙ originates from a merger of a BH and a helium star in a low-metallicity stellar environment in the Galactic halo. We constrain that only ∼0.006% of the total Galactic halo mass (including dark matter) can be hidden in the form of stellar origin BHs. These BHs cannot be detected by current observational surveys. We calculated the merger rates for current Galactic double compact objects (DCOs) for two considered common-envelope models: ∼3–81 Myr⁻¹ for BH-BH, ∼1–9 Myr⁻¹ for BH-neutron star (NS), and ∼14–59 Myr⁻¹ for NS-NS systems. We show the evolution of the merger rates of DCOs since the formation of the Milky Way until the current moment with the new star formation model of the Galaxy.