Black Holes in the Milky Way
Jessica Lu ✧ University of California, Berkeley, CA, USA
The Milky Way's black hole (BH) population is challenging to find outside of the 10s detected in accretion binary systems. Outside the Milky Way, merging BH binary populations are now found in large numbers through gravitational waves. Yet to fully interpret these results and place astrophysical constraints on the demographics, origin, and evolution of black holes, we require a more complete census of the isolated and binary black holes. We have embarked on a search for black holes in the Milky Way using advanced in high precision astrometry. This has allowed us to find and weigh isolated black holes that gravitationally lens background stars. Interestingly, the candidates found (out of 10 searched) are both low mass (); however the sample is too small to yet constrain population models. I will discuss these results and the landscape of planned and proposed missions, including Roman, ELTs, and a new CubeSat constellation concept called CuRIOS, to find and more precisely measure black hole and neutron star microlensing events. We have also found intermediate mass () black hole candidates in astrometric binaries at the Galactic Center. While these need to be confirmed with spectroscopy, such black holes may be expected from theories of dynamical formation and successive mergers in this dense region. Such systems may be detectable through microlensing and self-lensing as well. As samples of BHs in the Milky Way expand, we show through simulations that we can constrain their binary fraction, kick velocity distribution, and the initial-final mass relation.
