ARI Special Colloquium
Upcoming events
TBD
Rainer Weinberger (AIP)
ARI Special Colloquium
Astronomisches Rechen-Institut, Mönchhofstraße 12-14 [room in talk description], ARI library lounge
Rainer Weinberger (AIP)
ARI Special Colloquium
Astronomisches Rechen-Institut, Mönchhofstraße 12-14 [room in talk description], ARI library lounge
TBD
Lachlan Lancaster (CCA)
ARI Special Colloquium
Astronomisches Rechen-Institut, Mönchhofstraße 12-14 [room in talk description], ARI library lounge
Lachlan Lancaster (CCA)
ARI Special Colloquium
Astronomisches Rechen-Institut, Mönchhofstraße 12-14 [room in talk description], ARI library lounge
Past events
2026-04-01
14:00
14:00
Intermediate mass black holes and gravitational waves from dense hierarchically assembling high redshift star clusters
Antti Rantala (KICC)
ARI Special Colloquium
Astronomisches Rechen-Institut, Mönchhofstraße 12-14 [room in talk description], ARI seminar room on the first floor
Show/hide abstract
Abstract
We explore the formation of intermediate mass black holes (IMBHs), potential seeds for supermassive black holes (SMBHs), via runaway stellar collisions for a wide range of star cluster densities and metallicities. Our sample of isolated (>1400) and hierarchical (30) simulations of massive JWST z~10 analogue star clusters with up to 1.8 million stars includes collisional stellar dynamics, stellar evolution, and post-Newtonian equations of motion for black holes using the BIFROST code. High stellar wind rates suppress IMBH formation at high metallicities (above 0.2 of the solar value) and low collision rates prevent their formation at low densities. The assumptions about stellar wind loss rates strongly affect the final IMBH masses (6000 vs 25000 solar masses). We present fitting formulae for IMBH masses as a function of host star cluster properties, and formulate a simple model for the cosmic IMBH formation rate density. We highlight the current model uncertainties and emphasize the need for collaboration between the galaxy formation and stellar communities for future progress in IMBH science. Finally, we find that the characteristic gravitational wave (GW) fingerprint of hierarchical star cluster assembly is a close-to-equal mass GW merger in the IMBH mass range.
Antti Rantala (KICC)
ARI Special Colloquium
Astronomisches Rechen-Institut, Mönchhofstraße 12-14 [room in talk description], ARI seminar room on the first floor
Show/hide abstract
Abstract
We explore the formation of intermediate mass black holes (IMBHs), potential seeds for supermassive black holes (SMBHs), via runaway stellar collisions for a wide range of star cluster densities and metallicities. Our sample of isolated (>1400) and hierarchical (30) simulations of massive JWST z~10 analogue star clusters with up to 1.8 million stars includes collisional stellar dynamics, stellar evolution, and post-Newtonian equations of motion for black holes using the BIFROST code. High stellar wind rates suppress IMBH formation at high metallicities (above 0.2 of the solar value) and low collision rates prevent their formation at low densities. The assumptions about stellar wind loss rates strongly affect the final IMBH masses (6000 vs 25000 solar masses). We present fitting formulae for IMBH masses as a function of host star cluster properties, and formulate a simple model for the cosmic IMBH formation rate density. We highlight the current model uncertainties and emphasize the need for collaboration between the galaxy formation and stellar communities for future progress in IMBH science. Finally, we find that the characteristic gravitational wave (GW) fingerprint of hierarchical star cluster assembly is a close-to-equal mass GW merger in the IMBH mass range.
