Formation of massive seed black holes via collisions and accretion

Boekholt, Tjarda; Schleicher, Dominik R. G.; Fellhauer, M.; Klessen, Ralf S.; Reinoso, B.; Stutz, Amelia M.; Haemmerlé, L.

doi:10.1093/mnras/sty208

Cited by 91 publications

(62 citation statements)

References 76 publications

(89 reference statements)

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“…Recently, it has been suggested that the photospheres of growing supermassive stars embedded within dense stellar clusters may greatly inflate, in analogy with supermassive stars which grow by rapid accretion in the atomicallycooled halo scenario. The resulting larger cross-section for mergers may then be able to boost the possible final mass of the central object formed by cluster collapse by an order of magnitude or more (Boekholt et al 2018). In this case, however, the structure of the star would similarly be more analogous to that of rapidly-accreting supermassive stars, and we would still expect a phase of hydrostatic nuclear-burning prior to collapse (Woods et al 2017).…”

Section: Discussionmentioning

confidence: 99%

On monolithic supermassive stars

Woods

Heger

Haemmerlé

2020

Monthly Notices of the Royal Astronomical Society

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Supermassive stars have been proposed as the progenitors of the massive (∼ 10 9 M ⊙ ) quasars observed at z ∼ 7. Prospects for directly detecting supermassive stars with next-generation facilities depend critically on their intrinsic lifetimes, as well as their formation rates. We use the 1D stellar evolution code Kepler to explore the theoretical limiting case of zero-metallicity, non-rotating stars, formed monolithically with initial masses between 10 kM ⊙ and 190 kM ⊙ . We find that stars born with masses between ∼ 60 kM ⊙ and ∼ 150 kM ⊙ collapse at the end of the main sequence, burning stably for ∼ 1.5 Myr. More massive stars collapse directly through the general relativistic instability after only a thermal timescale of ∼ 3 kyr-4 kyr. The expected difficulty in producing such massive, thermally-relaxed objects, together with recent results for currently preferred rapidly-accreting formation models, suggests that such "truly direct" or "dark" collapses may not be typical for supermassive objects in the early Universe. We close by discussing the evolution of supermassive stars in the broader context of massive primordial stellar evolution and the possibility of supermassive stellar explosions.

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Section: Discussionmentioning

confidence: 99%

On monolithic supermassive stars

Woods

Heger

Haemmerlé

2020

Monthly Notices of the Royal Astronomical Society

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“…Stacy et al 2010Riaz et al 2018), and mergers (e.g. Stacy et al 2010;Greif et al 2012;Hosokawa et al 2016;Stacy et al 2016;Reinoso et al 2018;Boekholt et al 2018;Susa 2019). We refrain from exploring the properties of binaries or multiple systems since it is likely that they continue to change over the course of the simulation and we cover only a short time in our runs compared to other studies that have tackled this question (e.g.…”

Section: Stellar Encounter and Mergingmentioning

confidence: 99%

Formation sites of Population III star formation: The effects of different levels of rotation and turbulence on the fragmentation behaviour of primordial gas

Wollenberg

Glover

Clark

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We use the moving-mesh code arepo to investigate the effects of different levels of rotation and turbulence on the fragmentation of primordial gas and the formation of Population III stars. We consider 9 different combinations of turbulence and rotation and carry out 5 different realizations of each setup, yielding one of the largest sets of simulations of Population III star formation ever performed. We find that fragmentation in Population III star-forming systems is a highly chaotic process and show that the outcomes of individual realizations of the same initial conditions often vary significantly. However, some general trends are apparent. Increasing the turbulent energy promotes fragmentation, while increasing the rotational energy inhibits fragmentation. Within the ∼ 1000 yr period that we simulate, runs including turbulence yield flat protostellar mass functions while purely rotational runs show a more top-heavy distribution. The masses of the individual protostars are distributed over a wide range from a few 10 −3 M to several tens of M . The total mass growth rate of the stellar systems remains high throughout the simulations and depends only weakly on the degree of rotation and turbulence. Mergers between protostars are common, but predictions of the merger fraction are highly sensitive to the criterion used to decide whether two protostars should merge. Previous studies of Population III star formation have often considered only one realization per set of initial conditions. However, our results demonstrate that robust trends can only be reliably identified by considering averages over a larger sample of runs.

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“…If young binaries are embedded in a dense stellar cluster, the efficient three body scattering with the cluster member stars may efficiently work to reduce the binary separations. Such dense clusters are expected to form in slightly metal-enriched halos in the early universe (Katz et al 2015;Kashiyama & Inayoshi 2016;Sakurai et al 2017;Reinoso et al 2018;Boekholt et al 2018).…”

Section: Normal Pop III Star Formationmentioning

confidence: 99%

Forming Pop III binaries in self-gravitating discs: how to keep the orbital angular momentum

Chon

Hosokawa

2019

Monthly Notices of the Royal Astronomical Society

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The disk fragmentation is a possible process leading to the formation of Population III stellar binary systems. However, numerical simulations show diverse fates of the fragments; some evolve into stable binaries and others merge away with a central star.To clarify the physics behind such diversity, we perform a series of three dimensional hydrodynamics simulations in a controlled manner. We insert a point particle mimicking a fragment in a self-gravitating disk, where the initial mass and position are free parameters, and follow the orbital evolution for several tens of orbits. The results show great diversity even with such simple experiments. Some particles shortly merge away after migrating inward, but others survive as the migration stalls with the gapopening in the disk. We find that our results are well interpreted postulating that the orbital angular momentum is extracted by (i) the gravitational torque from the disk spiral structure, and (ii) tidal disruption of a gravitationally-bound envelope around the particle. Our analytic evaluations show the processes (i) and (ii) are effective in an outer and inner part of the disk respectively. There is a window of the gap-opening in the middle, if the envelope mass is sufficiently large. These all agree with our numerical results. We further show that the binaries, which appear for the "survival" cases, gradually expand while accreting the disk gas. Our theoretical framework is freely scalable to be applied for the present-day star and planet formation.

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Formation of massive seed black holes via collisions and accretion

Cited by 91 publications

References 76 publications

On monolithic supermassive stars

On monolithic supermassive stars

Formation sites of Population III star formation: The effects of different levels of rotation and turbulence on the fragmentation behaviour of primordial gas

Forming Pop III binaries in self-gravitating discs: how to keep the orbital angular momentum

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