Formation channels of single and binary stellar-mass black holes

TL;DR

This review explores the various formation channels of stellar-mass black holes, emphasizing recent progress and uncertainties in stellar evolution, binary interactions, and dynamical processes influencing black hole populations.

Contribution

It provides a comprehensive overview of both stellar evolution and dynamical formation channels of black holes, highlighting recent advances and remaining uncertainties.

Findings

Progress in understanding BBH mass and spin distributions

Dynamical processes can produce black holes in the mass gap

Uncertainties in stellar evolution affect black hole demographics

Abstract

These are exciting times for binary black hole (BBH) research. LIGO and Virgo detections are progressively drawing a spectacular fresco of BBH masses, spins and merger rates. In this review, we discuss the main formation channels of BBHs from stellar evolution and dynamics. Uncertainties on massive star evolution (e.g., stellar winds, rotation, overshooting and nuclear reaction rates), core-collapse supernovae and pair instability still hamper our comprehension of the mass spectrum and spin distribution of black holes (BHs), but substantial progress has been done in the field over the last few years. On top of this, the efficiency of mass transfer in a binary system and the physics of common envelope substantially affect the final BBH demography. Dynamical processes in dense stellar systems can trigger the formation of BHs in the mass gap and intermediate-mass BHs via hierarchical BH mergers and via multiple stellar collisions. Finally, we discuss the importance of reconstructing the cosmic evolution of BBHs.