Maximally accreting supermassive stars: a fundamental limit imposed by hydrostatic equilibrium
Context: Major mergers of gas-rich galaxies provide promising conditions for the formation of supermassive black holes (SMBHs; ≳105 M⊙) by direct collapse because they can trigger mass inflows as high as 104 − 105 M⊙ yr−1 on sub-parsec scales. However, the channel of SMBH formation in this case, eit...
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| Main Authors: | , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
02 December 2019
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| In: |
Astronomy and astrophysics
Year: 2019, Volume: 632 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201936716 |
| Online Access: | Verlag, Volltext: https://doi.org/10.1051/0004-6361/201936716 Verlag: https://www.aanda.org/articles/aa/abs/2019/12/aa36716-19/aa36716-19.html 
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| Author Notes: | L. Haemmerlé, G. Meynet, L. Mayer, R.S. Klessen, T.E. Woods, and A. Heger |
| Summary: | Context: Major mergers of gas-rich galaxies provide promising conditions for the formation of supermassive black holes (SMBHs; ≳105 M⊙) by direct collapse because they can trigger mass inflows as high as 104 − 105 M⊙ yr−1 on sub-parsec scales. However, the channel of SMBH formation in this case, either dark collapse (direct collapse without prior stellar phase) or supermassive star (SMS; ≳104 M⊙), remains unknown. Aims: Here, we investigate the limit in accretion rate up to which stars can maintain hydrostatic equilibrium. Methods: We compute hydrostatic models of SMSs accreting at 1–1000 M⊙ yr−1, and estimate the departures from equilibrium a posteriori by taking into account the finite speed of sound. Results: We find that stars accreting above the atomic cooling limit (≳10 M⊙ yr−1) can only maintain hydrostatic equilibrium once they are supermassive. In this case, they evolve adiabatically with a hylotropic structure, that is, entropy is locally conserved and scales with the square root of the mass coordinate. Conclusions: Our results imply that stars can only become supermassive by accretion at the rates of atomically cooled haloes (∼0.1 − 10 M⊙ yr−1). Once they are supermassive, larger rates are possible. |
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| Item Description: | Gesehen am 24.01.2020 |
| Physical Description: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201936716 |