Effects of turbulence and rotation on protostar formation as a precursor of massive black holes

Borm, C. Van; Bovino, S.; Latif, Muhammad; Schleicher, Dominik R. G.; Spaans, Marco

doi:10.1051/0004-6361/201424658

Cited by 24 publications

(32 citation statements)

References 128 publications

(164 reference statements)

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“…At densities > 10 −4 g/cm 3 , we reach the resolution limit of our simulations but we expect a close to adiabatic evolution in this regime. In spite of these differences, our results for the thermal and chemical properties are quite similar to and Van Borm et al (2014) because of the self-similar behavior of the isothermal run-away collapse.…”

Section: Thermal and Chemical Propertiessupporting

confidence: 63%

“…The net cooling rate can be approximated as (Omukai 2001;Schleicher et al 2010;Van Borm et al 2014):…”

Section: Chemical Modelmentioning

confidence: 99%

“…They found that although fragmentation is not completely suppressed, large inflow rates may lead to the formation of a supermassive star. On the other hand, improving on previous works and Van Borm et al (2014) performed 3D simulations starting from idealised initial conditions (a spherical gas cloud with a top hat density profile) which included turbulence and rotation as well as H − cooling and opacities for the H − bound-free emission, free-free absorption and the Rayleigh scattering of hydrogen atoms. They found that no strong fragmentation occurs under these conditions.…”

Section: Introductionmentioning

confidence: 99%

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Witnessing the birth of a supermassive protostar

Latif

Schleicher²,

Hartwig

2016

Mon. Not. R. Astron. Soc.

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The detection of z > 6 quasars reveals the existence of supermassive black holes of a few 10 9 M ⊙ . One of the potential pathways to explain their formation in the infant universe is the so-called direct collapse model which provides massive seeds of 10 5 − 10 6 M ⊙ . An isothermal direct collapse mandates that halos should be of a primordial composition and the formation of molecular hydrogen remains suppressed in the presence of a strong Lyman Werner flux. In this study, we perform high resolution cosmological simulations for two massive primordial halos employing a detailed chemical model which includes H − cooling as well as realistic opacities for both the bound-free H − emission and the Rayleigh scattering of hydrogen atoms. We are able to resolve the collapse up to unprecedentedly high densities of ∼ 10 −3 g/cm 3 and to scales of about 10 −4 AU. Our results show that the gas cools down to ∼ 5000 K in the presence of H − cooling, and induces fragmentation at scales of about 8000 AU in one of the two simulated halos, which may lead to the formation of a binary. In addition, fragmentation also occurs on the AU scale in one of the halos but the clumps are expected to merge on short time scales. Our results confirm that H − cooling does not prevent the formation of a supermassive star and the trapping of cooling radiation stabilises the collapse on small scales.

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Section: Thermal and Chemical Propertiessupporting

confidence: 63%

“…The net cooling rate can be approximated as (Omukai 2001;Schleicher et al 2010;Van Borm et al 2014):…”

Section: Chemical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Witnessing the birth of a supermassive protostar

Latif

Schleicher²,

Hartwig

2016

Mon. Not. R. Astron. Soc.

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“…If molecular hydrogen cooling is inhibited in these massive primordial haloes by strong ultra-violet radiation, a gas cloud gravitationally collapses via atomic hydrogen cooling nearly isothermally at T 8000 K (e.g., Omukai 2001). An embryo protostar eventually forms and begins to grow via gas accretion from a surrounding envelope (e.g., Inayoshi, Omukai & Tasker 2014;Van Borm et al 2014), analogous to normal Population III star formation (Yoshida, Omukai & Hernquist 2008). The accretion rate at this stage has the well-known temperature dependenceṀ * ∼ …”

Section: Introductionmentioning

confidence: 99%

Formation of primordial supermassive stars by burst accretion

Sakurai

Hosokawa

Yoshida

et al. 2015

Mon. Not. R. Astron. Soc.

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Recent observations show that supermassive black holes (SMBHs) with ∼ 10 9 M exist at redshift z 6; how they form has yet to be explained. A promising formation channel is the so-called direct collapse model, which posits that a massive seed BH forms through gravitational collapse of a ∼ 10 5 M supermassive star. We study the evolution of such a supermassive star growing by rapid mass accretion. The internal stellar structure is also followed consistently in our calculation. In particular, we examine the impact of time-dependent mass accretion of repeating burst and quiescent phases that are expected to occur with a self-gravitating circumstellar disk. We show that the stellar evolution with such episodic accretion differs qualitatively from that expected with a constant accretion rate, even if the mean accretion rate is the same. Unlike the case of constant mass accretion, whereby the star expands roughly following R * 2.6 × 10 3 R (M * /100 M ) 1/2 , the protostar can substantially contract during the quiescent phases between accretion bursts. The stellar effective temperature and ionizing photon emissivity increase accordingly as the star contracts, which can cause strong ionizing feedback and halt the mass accretion onto the star. With a fixed duration of the quiescent phase ∆t q , such contraction occurs in early evolutionary phases, i.e. for M * 10 3 M with ∆t q 10 3 yr. For later epochs and larger masses but the same ∆t q , contraction is negligible even during quiescent phases. With larger quiescent times ∆t q , however, the star continues to contract during quiescent phases even for the higher stellar masses. We show that such behavior is well understood by comparing the interval time and the thermal relaxation time for a bloated surface layer. We conclude that the UV radiative feedback becomes effective if the quiescent phase associated by the burst accretion is longer than ∼ 10 3 yr, which is possible in an accretion disk forming in the direct collapse model.

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“…In such a case, the dominant coolant is atomic hydrogen (Omukai 2001;Oh & Haiman 2002), and the gas follows a nearly isothermal collapse at temperatures around the virial value T vir 10 4 K: first, due to Lyman-α cooling up to densities n H 10 6 cm −3 , where the gas be-comes optically thick to Lyα radiation, and then due to H − bound-free and free-free emission (Regan & Haehnelt 2009;Latif et al 2013b;Inayoshi et al 2014;Becerra et al 2015Becerra et al , 2018Chon et al 2016). As the gas keeps contracting, it becomes optically thick to H − continuum emission around n H 10 17 cm −3 , at which point the gas evolves adiabatically and forms a massive protostar at the center of the halo (Inayoshi et al 2014;Van Borm et al 2014;Becerra et al 2015;. Since the accretion rate in a Jeansunstable cloud scales as M ∝ T 3/2 and the gas in an atomic cooling halo can reach temperatures T 10 4 K, very high values for the accretion rate ( 1 M yr −1 ) are achieved.…”

Section: Introductionmentioning

confidence: 99%

Assembly of supermassive black hole seeds

Becerra

Marinacci

Hernquist

2018

Monthly Notices of the Royal Astronomical Society

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We present a suite of six fully cosmological, three-dimensional simulations of the collapse of an atomic cooling halo in the early Universe. We use the moving-mesh code arepo with an improved primordial chemistry network to evolve the hydrodynamical and chemical equations. The addition of a strong Lyman-Werner background suppresses molecular hydrogen cooling and permits the gas to evolve nearly isothermally at a temperature of about 8000 K. Strong gravitational torques effectively remove angular momentum and lead to the central collapse of gas, forming a supermassive protostar at the center of the halo. We model the protostar using two methods: sink particles that grow through mergers with other sink particles, and a stiff equation of state that leads to the formation of an adiabatic core. We impose threshold densities of 10 8 , 10 10 , and 10 12 cm −3 for the sink particle formation and the onset of the stiff equation of state to study the late, intermediate, and early stages in the evolution of the protostar, respectively. We follow its growth from masses 10 M to 10 5 M , with an average accretion rate of M 2 M yr −1 for sink particles, and 0.8−1.4 M yr −1 for the adiabatic cores. At the end of the simulations, the Hii region generated by radiation from the central object has long detached from the protostellar photosphere, but the ionizing radiation remains trapped in the inner host halo, and has thus not yet escaped into the intergalactic medium. Fully coupled, radiation-hydrodynamics simulations hold the key for further progress.

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Effects of turbulence and rotation on protostar formation as a precursor of massive black holes

Cited by 24 publications

References 128 publications

Witnessing the birth of a supermassive protostar

Witnessing the birth of a supermassive protostar

Formation of primordial supermassive stars by burst accretion

Assembly of supermassive black hole seeds

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