The Cosmic Evolution of Binary Black Holes in Young, Globular and Nuclear Star Clusters: Rates, Masses, Spins and Mixing Fractions

Understand

The growing population of binary black holes (BBHs) observed by gravitational wave detectors is a potential Rosetta stone for understanding their formation channels.

• Here, we use an upgraded version of our semi-analytic codes {\sc fastcluster} and {\sc cosmo$\mathcal{R}$ate} to investigate the cosmic evolution of four different BBH populations: isolated BBHs and dynamically formed BBHs in nuclear star clusters (NSCs), globular clusters (GCs), and young star clusters (YSCs).
• With our approach, we can study different channels assuming the same stellar and binary input physics.
• We find that the merger rate density of BBHs in GCs and NSCs is barely affected by stellar metallicity ($Z$), while the rate of isolated BBHs changes wildly with $Z$.