Kolloquien
Wintersemester 2023/2024
URL to ICS calendar of this seminar
Kirchhoff-Institut für Physik, Otto-Haxel-Hörsaal
Friday 17:15
Talks
24.11.2023 17:00
KIP, INF 227, Hörsaal 1

The number of gravitational-wave detections approaches the 100 mark and starts
revealing the big picture of binary black hole populations. Several detected black holes
have mass in the lower (2-5 Msun) or upper (~60-120 Msun) mass gap, challenging
models of stellar and binary evolution. Furthermore, evidence for unequal-mass
systems and non-negligible spin misalignment advocate for unconventional scenarios
of binary black hole formation. We recently proposed that the mass function of the
LIGO-Virgo black holes evolves with redshift. This result, if confirmed, favours
scenarios in which the properties of black hole progenitors and their birth environment
change across cosmic time. One key aspect is the metallicity of the progenitor star: a
metal-poor environment enhances the formation of massive black holes (>20 Msun)
and boosts their merger rate via stable mass transfer. Moreover, formation in a
globular cluster environment leads to a great variety of unconventional features in
binary black holes: hierarchical mergers favour the formation of oversize black holes
and close gravitational encounters randomize their spin orientations. Next-generation
gravitational-wave detectors will mark a turning point to interpret the formation of
binary black holes, by observing their mergers at cosmic dawn.