From Young Massive Clusters to Old Globular Clusters: Density Profile Evolution and Intermediate-mass Black Hole Formation
The surface brightness profiles of globular clusters are conventionally described with the well-known King profile. However, observations of young massive clusters (YMCs) in the local Universe suggest that they are better fit by simple models with flat central cores and simple power-law densities in...
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2025-01-01
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| author | Kuldeep Sharma Carl L. Rodriguez |
| author_facet | Kuldeep Sharma Carl L. Rodriguez |
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| description | The surface brightness profiles of globular clusters are conventionally described with the well-known King profile. However, observations of young massive clusters (YMCs) in the local Universe suggest that they are better fit by simple models with flat central cores and simple power-law densities in their outer regions (such as the Elson-Fall-Freeman, or EFF, profile). Depending on their initial central density, YMCs may also facilitate large numbers of stellar collisions, potentially creating very massive stars that will directly collapse into intermediate-mass black holes (IMBHs). Using Monte Carlo N -body models of YMCs, we show that EFF-profile clusters transform to Wilson or King profiles through natural dynamical evolution, but that their final W _0 parameters do not strongly correlate to their initial concentrations. In the densest YMCs, runaway stellar mergers can produce stars that collapse into IMBHs, with their final masses depending on the treatment of the giant star envelopes during collisions. If a common-envelope prescription is assumed, where the envelope is partially or entirely lost, stars form with masses up to 824 M _⊙ , collapsing into IMBHs of 232 M _⊙ . Alternatively, if no mass loss is assumed, stars as massive as 4000 M _⊙ can form, collapsing into IMBHs of ∼4000 M _⊙ . In doing so, these runaway collisions also deplete the clusters of their primordial massive stars, reducing the number of stellar-mass BHs by as much as ∼40%. This depletion will accelerate the core collapse, suggesting that the process of IMBH formation itself may produce the high densities observed in some core-collapsed clusters. |
| format | Article |
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| publishDate | 2025-01-01 |
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| spelling | doaj-art-e059d2b79db7464fa84c40660d6185962025-08-20T02:13:19ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01983216210.3847/1538-4357/adbbdfFrom Young Massive Clusters to Old Globular Clusters: Density Profile Evolution and Intermediate-mass Black Hole FormationKuldeep Sharma0https://orcid.org/0000-0002-6675-0424Carl L. Rodriguez1https://orcid.org/0000-0003-4175-8881McWilliams Center for Cosmology, Carnegie Mellon University , 5000 Forbes Ave., Pittsburgh, PA 15213, USA ; kul.shar90@gmail.com; Department of Physics and Astronomy, University of North Carolina at Chapel Hill , 120 E. Cameron Ave., Chapel Hill, NC 27599, USADepartment of Physics and Astronomy, University of North Carolina at Chapel Hill , 120 E. Cameron Ave., Chapel Hill, NC 27599, USAThe surface brightness profiles of globular clusters are conventionally described with the well-known King profile. However, observations of young massive clusters (YMCs) in the local Universe suggest that they are better fit by simple models with flat central cores and simple power-law densities in their outer regions (such as the Elson-Fall-Freeman, or EFF, profile). Depending on their initial central density, YMCs may also facilitate large numbers of stellar collisions, potentially creating very massive stars that will directly collapse into intermediate-mass black holes (IMBHs). Using Monte Carlo N -body models of YMCs, we show that EFF-profile clusters transform to Wilson or King profiles through natural dynamical evolution, but that their final W _0 parameters do not strongly correlate to their initial concentrations. In the densest YMCs, runaway stellar mergers can produce stars that collapse into IMBHs, with their final masses depending on the treatment of the giant star envelopes during collisions. If a common-envelope prescription is assumed, where the envelope is partially or entirely lost, stars form with masses up to 824 M _⊙ , collapsing into IMBHs of 232 M _⊙ . Alternatively, if no mass loss is assumed, stars as massive as 4000 M _⊙ can form, collapsing into IMBHs of ∼4000 M _⊙ . In doing so, these runaway collisions also deplete the clusters of their primordial massive stars, reducing the number of stellar-mass BHs by as much as ∼40%. This depletion will accelerate the core collapse, suggesting that the process of IMBH formation itself may produce the high densities observed in some core-collapsed clusters.https://doi.org/10.3847/1538-4357/adbbdfIntermediate-mass black holesYoung star clusters |
| spellingShingle | Kuldeep Sharma Carl L. Rodriguez From Young Massive Clusters to Old Globular Clusters: Density Profile Evolution and Intermediate-mass Black Hole Formation The Astrophysical Journal Intermediate-mass black holes Young star clusters |
| title | From Young Massive Clusters to Old Globular Clusters: Density Profile Evolution and Intermediate-mass Black Hole Formation |
| title_full | From Young Massive Clusters to Old Globular Clusters: Density Profile Evolution and Intermediate-mass Black Hole Formation |
| title_fullStr | From Young Massive Clusters to Old Globular Clusters: Density Profile Evolution and Intermediate-mass Black Hole Formation |
| title_full_unstemmed | From Young Massive Clusters to Old Globular Clusters: Density Profile Evolution and Intermediate-mass Black Hole Formation |
| title_short | From Young Massive Clusters to Old Globular Clusters: Density Profile Evolution and Intermediate-mass Black Hole Formation |
| title_sort | from young massive clusters to old globular clusters density profile evolution and intermediate mass black hole formation |
| topic | Intermediate-mass black holes Young star clusters |
| url | https://doi.org/10.3847/1538-4357/adbbdf |
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