Rapid formation of a very massive star (&gt;50000 M <sub>⊙</sub> ), and subsequently, of an IMBH, from runaway collisions

Context . We present simulations of a massive young star cluster using the codes N body 6++GPU and MOCCA. The cluster is initially more compact than previously published models. It contains one million stars and has a total mass of 5.86 × 10 5 M ⊙ and a half-mass radius of 0.1 pc. Aims . We analyzed the formation and growth of a very massive star (VMS) through successive stellar collisions and investigated the subsequent formation of an intermediate-mass black hole (IMBH) in the core of a dense star cluster. Methods . We used direct N -body and Monte Carlo simulations that incorporated updated stellar evolution prescriptions for single and binary stellar evolution (SSE and BSE) tailored to massive stars and VMSs. These include revised treatments of stellar radii, rejuvenation, and mass loss during collisions. While the prescriptions represent reasonable extrapolations into the VMS regime, the internal structure and thermal state of VMSs that formed through stellar collisions remain uncertain, and future work may require further refinement. Results . Runaway stellar collisions in the cluster core produce a VMS that exceeds 5 × 10 4 M ⊙ within 5 Myr that subsequently collapses into an IMBH. We stress that further work on stellar astrophysics is needed, particularly in the context of VMS formation. The VMS formation currently represents strong uncertainties. Conclusions . Our model suggests that dense stellar environments may enable the formation of VMSs and massive black hole seeds through runaway stellar collisions. These results provide a potential pathway for early black hole growth in star clusters and offer a theoretical context for interpreting recent observations with the James Webb Space Telescope of young compact clusters at high redshift.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-11-12
DOI
https://doi.org/10.1051/0004-6361/202555307
Citations
4
Primary Topic
Astrophysics and Star Formation Studies
Type
article
Field-Weighted Citation Impact
4.62

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article

Rapid formation of a very massive star (>50000 M ⊙ ), and subsequently, of an IMBH, from runaway collisions

Francesco Flammini Dotti, Andrés Escala, Abbas Askar, Renyue Cen et al.
4 citations
Astronomy and Astrophysics
Astrophysics and Star Formation Studies
4.62
article

Rapid formation of a very massive star (>50000 M ⊙ ), and subsequently, of an IMBH, from runaway collisions

Francesco Flammini Dotti, Andrés Escala, Abbas Askar, Renyue Cen, Thorsten Naab, Manuel Arca Sedda, Mirek Giersz, C Vergara, Ataru Tanikawa, Nils Hoyer, Xiaoying Pang, Nadine Neumayer, Peter Berczik, Jarrod R. Hurley, Arkadiusz Hypki, Rainer Spurzem, R.G. Dominik Schleicher, W.H. Albrecht Kamlah
article en
4 citations

Abstract

Context . We present simulations of a massive young star cluster using the codes N body 6++GPU and MOCCA. The cluster is initially more compact than previously published models. It contains one million stars and has a total mass of 5.86 × 10 5 M ⊙ and a half-mass radius of 0.1 pc. Aims . We analyzed the formation and growth of a very massive star (VMS) through successive stellar collisions and investigated the subsequent formation of an intermediate-mass black hole (IMBH) in the core of a dense star cluster. Methods . We used direct N -body and Monte Carlo simulations that incorporated updated stellar evolution prescriptions for single and binary stellar evolution (SSE and BSE) tailored to massive stars and VMSs. These include revised treatments of stellar radii, rejuvenation, and mass loss during collisions. While the prescriptions represent reasonable extrapolations into the VMS regime, the internal structure and thermal state of VMSs that formed through stellar collisions remain uncertain, and future work may require further refinement. Results . Runaway stellar collisions in the cluster core produce a VMS that exceeds 5 × 10 4 M ⊙ within 5 Myr that subsequently collapses into an IMBH. We stress that further work on stellar astrophysics is needed, particularly in the context of VMS formation. The VMS formation currently represents strong uncertainties. Conclusions . Our model suggests that dense stellar environments may enable the formation of VMSs and massive black hole seeds through runaway stellar collisions. These results provide a potential pathway for early black hole growth in star clusters and offer a theoretical context for interpreting recent observations with the James Webb Space Telescope of young compact clusters at high redshift.

Astronomy and AstrophysicsVol. 704
National Academy of Sciences of Ukraine (UA), Tokyo University of the Arts (JP), University of Concepción (CL), Shanghai Normal University (CN), Heidelberg University (DE), Istituto Nazionale di Fisica Nucleare, Galileo Galilei Institute for Theoretical Physics (IT), Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Gran Sasso (IT), Max Planck Institute for Astrophysics (DE), Max Planck Institute for Astronomy (DE), Institute of Astronomy (RU), Collurania Teramo Observatory (IT), ARC Centre of Excellence for Gravitational Wave Discovery (AU), Main Astronomical Observatory (UA), Astronomical Institute of the Slovak Academy of Sciences (SK), Institute for Advanced Study (DE), Nicolaus Copernicus Astronomical Center (PL), Gran Sasso Science Institute (IT), National Astronomical Observatories (CN), Donostia International Physics Center (ES), New York University (US), Adam Mickiewicz University in Poznań (PL), Xi’an Jiaotong-Liverpool University (CN), University of Chile (CL), The University of Tokyo (JP), Sapienza University of Rome (IT), Netherlands Institute for Radio Astronomy (NL), Fukui Prefectural University (JP), Polish Academy of Sciences (PL)
National Science Foundation, International Max Planck Research School for Environmental, Cellular and Molecular Microbiology, European Commission, Deutscher Akademischer Austauschdienst, Deutsche Forschungsgemeinschaft, Universität Heidelberg, National Natural Science Foundation of China, Centro de Astrofísica y Tecnologías Afines, International Max Planck Research School for Advanced Methods in Process and Systems Engineering, Fondation Merac, Agencia Nacional de Investigación y Desarrollo, Gauss Centre for Supercomputing, Japan Society for the Promotion of Science, National Key Research and Development Program of China, National Astronomical Observatories, Chinese Academy of Sciences, Kavli Institute for Theoretical Physics, University of California, Santa Barbara
Openalex Percentile: Top 5%
Astrophysics and Star Formation Studies
4.62
DOIOpen Access PDFOpenAlex
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