A Caltech Library Service

Black Hole Mergers from Star Clusters with Top-heavy Initial Mass Functions

Weatherford, Newlin C. and Fragione, Giacomo and Kremer, Kyle and Chatterjee, Sourav and Ye, Claire S. and Rodriguez, Carl L. and Rasio, Frederic A. (2021) Black Hole Mergers from Star Clusters with Top-heavy Initial Mass Functions. Astrophysical Journal Letters, 907 (2). Art. No. L25. ISSN 2041-8213. doi:10.3847/2041-8213/abd79c.

[img] PDF - Published Version
See Usage Policy.

[img] PDF - Accepted Version
Creative Commons Attribution.


Use this Persistent URL to link to this item:


Recent observations of globular clusters (GCs) provide evidence that the stellar initial mass function (IMF) may not be universal, suggesting specifically that the IMF grows increasingly top-heavy with decreasing metallicity and increasing gas density. Noncanonical IMFs can greatly affect the evolution of GCs, mainly because the high end determines how many black holes (BHs) form. Here we compute a new set of GC models, varying the IMF within observational uncertainties. We find that GCs with top-heavy IMFs lose most of their mass within a few gigayears through stellar winds and tidal stripping. Heating of the cluster through BH mass segregation greatly enhances this process. We show that, as they approach complete dissolution, GCs with top-heavy IMFs can evolve into "dark clusters" consisting of mostly BHs by mass. In addition to producing more BHs, GCs with top-heavy IMFs also produce many more binary BH (BBH) mergers. Even though these clusters are short-lived, mergers of ejected BBHs continue at a rate comparable to, or greater than, what is found for long-lived GCs with canonical IMFs. Therefore, these clusters, though they are no longer visible today, could still contribute significantly to the local BBH merger rate detectable by LIGO/Virgo, especially for sources with higher component masses well into the BH mass gap. We also report that one of our GC models with a top-heavy IMF produces dozens of intermediate-mass black holes (IMBHs) with masses M > 100 M_⊙, including one with M > 100 M_⊙. Ultimately, additional gravitational wave observations will provide strong constraints on the stellar IMF in old GCs and the formation of IMBHs at high redshift.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Weatherford, Newlin C.0000-0002-9660-9085
Fragione, Giacomo0000-0002-7330-027X
Kremer, Kyle0000-0002-4086-3180
Chatterjee, Sourav0000-0002-3680-2684
Ye, Claire S.0000-0001-9582-881X
Rodriguez, Carl L.0000-0003-4175-8881
Rasio, Frederic A.0000-0002-7132-418X
Additional Information:© 2021 The American Astronomical Society. Received 2020 November 10; revised 2020 December 23; accepted 2020 December 29; published 2021 January 27. This work was supported by NSF grant AST-1716762 and through the computational resources and staff contributions provided for the Quest high-performance computing facility at Northwestern University. N.W. acknowledges support from the CIERA Riedel Family Graduate Fellowship as well as the NSF GK-12 Fellowship Program under Grant DGE-0948017. G.F. acknowledges support from a CIERA Fellowship. K.K. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-2001751. S.C. acknowledges support from the Department of Atomic Energy, Government of India, under project No. 12-R&D-TFR-5.02-0200.
Funding AgencyGrant Number
Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA)UNSPECIFIED
NSF Graduate Research FellowshipDGE-0948017
NSF Astronomy and Astrophysics FellowshipAST-2001751
Department of Atomic Energy (India)12-R&D-TFR-5.02-0200
Subject Keywords:Initial mass function ; Stellar mass black holes ; Globular star clusters ; Stellar dynamics ; N-body simulations ; Gravitational wave sources
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Initial mass function (796); Stellar mass black holes (1611); Globular star clusters (656); Stellar dynamics (1596); N-body simulations (1083); Gravitational wave sources (677)
Record Number:CaltechAUTHORS:20210127-123127177
Persistent URL:
Official Citation:Newlin C. Weatherford et al 2021 ApJL 907 L25
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107774
Deposited By: Tony Diaz
Deposited On:27 Jan 2021 20:44
Last Modified:16 Nov 2021 19:06

Repository Staff Only: item control page