Fragmentation inside atomic cooling haloes exposed to Lyman–Werner radiation

Regan, John A.; Downes, T. P.

doi:10.1093/mnras/sty134

Cited by 36 publications

(25 citation statements)

References 81 publications

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“…Regardless of this, both approaches show similar values for the mass and accretion rates of the central object, which are also consistent with results from previous works (e.g. Regan & Haehnelt 2009;Latif et al 2013b,c;Shlosman et al 2016;Regan & Downes 2018a). Therefore, we do not expect this to change our conclusions significantly.…”

Section: Caveatssupporting

confidence: 93%

“…For example, Regan & Haehnelt (2009) ;Latif et al (2013a); Choi et al (2015) used a pressure floor beyond a certain resolution level, which limited the maximum density to n H 10 6 − 10 12 cm −3 . Similarly, Latif et al (2013c); Shlosman et al (2016); Regan & Downes (2018a) employed sink particles that replace gas above a maximum density of n H 10 5 − 10 8 cm −3 . One disadvantage of these methods is the limited resolution in regions where density is highest, hence they only describe well the processes on large scales.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Caveatssupporting

confidence: 93%

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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“…In this study we have used the publicly available adaptive mesh refinement code Enzo 2 to study the birth of a massive black hole seed from a SMS. We have utilised the SmartStar particles introduced in Regan & Downes (2018a) and augmented them with subgrid prescriptions specific to a black hole seed as we now discuss.…”

Section: Numerical Frameworkmentioning

confidence: 99%

Super-Eddington accretion and feedback from the first massive seed black holes

Regan

Downes

Volonteri

et al. 2019

Monthly Notices of the Royal Astronomical Society

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108

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Super-Eddington accretion onto massive black hole seeds may be commonplace in the early Universe, where the conditions exist for rapid accretion. Direct collapse black holes are often invoked as a possible solution to the observation of super massive black holes (SMBHs) in the pre-reionisation Universe. We investigate here how feedback, mainly in the form of bipolar jets, from super-Eddington accreting seed black holes will affect their subsequent growth. We find that, nearly independent of the mass loading of the bipolar jets, the violent outflows generated by the jets evacuate a region of approximately 0.1 pc surrounding the black hole seed. However, the jet outflows are unable to break free of the halo and their impact is limited to the immediate vicinity of the black hole. The outflows suppress any accretion for approximately a dynamical time. The gas then cools, recombines and falls back to the centre where high accretion rates are again observed. The overall effect is to create an effective accretion rate with values of between 0.1 and 0.5 times the Eddington rate. If this episodic accretion rate is maintained for order 500 million years then the black hole will increase in mass by a factor of between 3 and 300 but far short of the factor of 10 4 required for the seeds to become the SMBHs observed at z > 6. Therefore, direct collapse black holes born into atomic cooling haloes and which experience strong negative mechanical feedback will require external influences (e.g. rapid major mergers with other haloes) to promote efficient accretion and reach SMBH masses within a few hundred million years.

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“…The collapsing flow must also be prevented from forming the molecular hydrogen. Otherwise, the H 2 cooling can lead to fragmentation and formation of Pop III stars, thus preventing formation of a massive central black hole seed (Haiman et al 2000;Wise & Abel 2008;Begelman & Shlosman 2009;Regan & Haehnelt 2009;Greif et al 2011;Latif et al 2016;Regan & Downes 2018). Numerical simulations of an optically-thin collapse have confirmed that in the absence of a molecular cooling, the gas stays isothermal, at the atomic hydrogen cooling floor (Omukai 2001;Bromm & Loeb 2003;Shang et al 2010;Choi et al 2013Choi et al , 2015Latif et al 2013;Choi et al 2013;Latif et al 2016;Shlosman et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Direct collapse to supermassive black hole seeds: the critical conditions for suppression of H2 cooling

Luo

Shlosman

Nagamine

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Observations of high-redshift quasars imply the presence of supermassive black holes (SMBHs) already at z ∼ 7.5. An appealing and promising pathway to their formation is the direct collapse scenario of a primordial gas in atomic-cooling haloes at z ∼ 10 − 20, when the H 2 formation is inhibited by a strong background radiation field, whose intensity exceeds a critical value, J crit . To estimate J crit , idealized spectra have been assumed, with a fixed ratio of H 2 photo-dissociation rate k H 2 to the H − photodetachment rate k H − . This assumption, however, could be too narrow in scope as the nature of the background radiation field is not known precisely. In this work we show that the critical condition for suppressing the H 2 cooling in the collapsing gas could be described in a more general way by a combination of k H 2 and k H − parameters, without any additional assumptions about the shape of the underlying radiation spectrum. By performing a series of cosmological zoom-in simulations with an encompassing set of k H 2 and k H − , we examine the gas flow by following evolution of basic parameters of the accretion flow. We test under what conditions the gas evolution is dominated by H 2 and/or atomic cooling. We confirm the existence of a critical curve in the k H 2 − k H − plane, and provide an analytical fit to it. This curve depends on the conditions in the direct collapse, and reveals domains where the atomic cooling dominates over the molecular cooling. Furthermore, we have considered the effect of H 2 self-shielding on the critical curve, by adopting three methods for the effective column density approximation in H 2 . We find that the estimate of the characteristic length-scale for shielding can be improved by using λ Jeans25 , which is 0.25 times that of the local Jeans length.

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Fragmentation inside atomic cooling haloes exposed to Lyman–Werner radiation

Cited by 36 publications

References 81 publications

Assembly of supermassive black hole seeds

Assembly of supermassive black hole seeds

Super-Eddington accretion and feedback from the first massive seed black holes

Direct collapse to supermassive black hole seeds: the critical conditions for suppression of H2 cooling

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