On the Prevalence of Supermassive Black Holes over Cosmic Time

Buchner, Johannes; Treister, Ezequiel; Bauer, F. E.; Sartori, Lia F.; Schawinski, Kevin

doi:10.3847/1538-4357/aafd32

Cited by 25 publications

(15 citation statements)

References 73 publications

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“…Some observational campaigns confirm this (e.g., Kim et al 2009;Husband et al 2013), while others don't (Morselli et al 2014;Mazzucchelli et al 2017). The discrepancy in results may arise due to various selection effects, low-number statistics and stochasticity (Buchner et al 2019). In addition, the host galaxies of high-redshift quasars tend to have very high star formation rates (SFR; Trakhtenbrot et al 2017;Decarli et al 2018), indicating high gas content.…”

Section: Smbh Propertiesmentioning

confidence: 93%

High-redshift SMBHs can grow from stellar-mass seeds via chaotic accretion

Zubovas

King

2021

Monthly Notices of the Royal Astronomical Society

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Extremely massive black holes, with masses $M_{\rm BH} \gt 10^9 {\, \rm M_{\odot }}$, have been observed at ever higher redshifts. These results create ever tighter constraints on the formation and growth mechanisms of early black holes. Here we show that even the most extreme black hole known, Pōniuā’ena, can grow from a $10 {\, \rm M_{\odot }}$ seed black hole via Eddington-limited luminous accretion, provided that accretion proceeds almost continuously, but is composed of a large number of episodes with individually uncorrelated initial directions. This chaotic accretion scenario ensures that the growing black hole spins slowly, with the dimensionless spin parameter $a \lower.5ex\hbox{$\,\, \buildrel\lt \over \sim \,\,$}0.2$, so its radiative efficiency is also low, ϵ ≃ 0.06. If accretion is even partially aligned, with $20\!-\!40{{\ \rm per\ cent}}$ of accretion events happening in the same direction, the black hole spin and radiative efficiency are much higher, leading to significantly slower growth. We suggest that the chaotic accretion scenario can be completely falsified only if a $10^9 {\, \rm M_{\odot }}$ black hole is discovered at z ≥ 9.1, approximately 150 Myr before Pōniuā’ena. The space density of extreme quasars suggests that only a very small fraction, roughly one in 4 × 107, of seed black holes need to encounter favourable growth conditions to produce the observed extreme quasars. Other seed black holes grow much less efficiently, mainly due to lower duty cycles, so are much more difficult to detect.

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Section: Smbh Propertiesmentioning

confidence: 93%

High-redshift SMBHs can grow from stellar-mass seeds via chaotic accretion

Zubovas

King

2021

Monthly Notices of the Royal Astronomical Society

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“…PHYSICAL PICTURE The SMBHs of ∼ 10 9 M ⊙ at z ∼ 6 are rare objects of an abundance ∼ 1 Gpc −3 , and thus rare conditions may be required to explain their formation (e.g. Buchner et al 2019). The situation we consider is similar to the usual direct collapse scenario (e.g.…”

Section: Introductionmentioning

confidence: 99%

Making a Supermassive Star by Stellar Bombardment

Tagawa

Haiman

Kocsis

2020

ApJ

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Approximately two hundred supermassive black holes (SMBHs) have been discovered within the first ∼Gyr after the Big Bang. One pathway for the formation of SMBHs is through the collapse of supermassive stars (SMSs). A possible obstacle to this scenario is that the collapsing gas fragments and forms a cluster of main sequence stars. Here we raise the possibility that stellar collisions may be sufficiently frequent and energetic to inhibit the contraction of the massive protostar, avoiding strong UV radiation driven outflows, and allowing it to continue growing into a SMS. We investigate this scenario with semi-analytic models incorporating star formation, gas accretion, dynamical friction from stars and gas, stellar collisions, and gas ejection. We find that when the collapsing gas fragments at a density of 3 × 10 10 cm −3 , the central protostar contracts due to infrequent stellar mergers, and in turn photo-evaporates the remaining collapsing gas, resulting in the formation of 10 4 M ⊙ object. On the other hand, when the collapsing gas fragments at higher densities (expected for a metal-poor cloud with Z 10 −5 Z ⊙ with suppressed H 2 abundance) the central protostar avoids contraction and keeps growing via frequent stellar mergers, reaching masses as high as ∼ 10 5 − 10 6 M ⊙ . We conclude that frequent stellar mergers represent a possible pathway to form massive BHs in the early universe.

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“…This result eases tension in models finding strong clustering conditions around quasars with assumed ε DC ∼ 1. These are typical outputs from using simpler models for populating halos with galaxies, such as assigning Lymanbreak galaxies through a constant halo mass cut (Romano-Diaz et al 2011;Buchner et al 2019). In these instances, the use of a halo mass cut does not consider the event where the massive surrounding halos may be self-regulated, thus leading to an overestimation of visible galaxy neighbours.…”

Section: The Diversity Of Environments Around Luminous Quasarsmentioning

confidence: 99%

The Diversity of Environments Around Luminous Quasars at Redshift $z \sim 6$

Ren,

Trenti,

Marshall

et al. 2021

Preprint

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Significant clustering around the rarest luminous quasars is a feature predicted by dark matter theory combined with number density matching arguments. However, this expectation is not reflected by observations of quasars residing in a diverse range of environments. Here, we assess the tension in the diverse clustering of visible i-band dropout galaxies around luminous z ∼ 6 quasars. Our approach uses a simple empirical method to derive the median luminosity to halo mass relation, L c (M h ) for both quasars and galaxies under the assumption of log-normal luminosity scatter, Σ Q and Σ G . We show that higher Σ Q reduces the average halo mass hosting a quasar of a given luminosity, thus introducing at least a partial reversion to the mean in the number count distribution of nearby Lyman-Break galaxies. We generate a large sample of mock Hubble Space Telescope fields-of-view centred across rare z ∼ 6 quasars by resampling pencil beams traced through the dark matter component of the BlueTides cosmological simulation. We find that diverse quasar environments are expected for Σ Q > 0.4, consistent with numerous observations and theoretical studies. However, we note that the average number of galaxies around the central quasar is primarily driven by galaxy evolutionary processes in neighbouring halos, as embodied by our parameter Σ G , instead of a difference in the large scale structure around the central quasar host, embodied by Σ Q . We conclude that models with Σ G > 0.3 are consistent with current observational constraints on high-z quasars, and that such a value is comparable to the scatter estimated from hydrodynamical simulations of galaxy formation.

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On the Prevalence of Supermassive Black Holes over Cosmic Time

Cited by 25 publications

References 73 publications

High-redshift SMBHs can grow from stellar-mass seeds via chaotic accretion

High-redshift SMBHs can grow from stellar-mass seeds via chaotic accretion

Making a Supermassive Star by Stellar Bombardment

The Diversity of Environments Around Luminous Quasars at Redshift $z \sim 6$

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