The seeds of supermassive black holes and the role of local radiation and metal spreading

Maio, Umberto; Borgani, S.; Ciardi, B.; Petkova, Margarita

doi:10.1017/pasa.2019.10

Cited by 21 publications

(24 citation statements)

References 177 publications

(327 reference statements)

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“…The effects of alternative choices are small in thin media, but become important in dense sites (e.g. when estimating molecular cooling of collapsing gas or critical fluxes of impinging radiation during the formation of massive black-hole seeds; Luo et al 2020;Maio et al 2019). Neglecting HI shielding corrections at high redshift (z > 5) leads to a large degree of H ionisation and H 2 photodissociation, causing underestimation of HI and H 2 cosmological densities and leading to a trend of the atomic and molecular density parameters in tension with data even at z < 5.…”

Section: Discussionmentioning

confidence: 99%

Atomic and molecular gas from the epoch of reionisation down to redshift 2

Maio

Péroux

Ciardi

2022

A&A

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Context. Cosmic gas makes up about 90% of the baryonic matter in the Universe and H2 molecule is the most tightly linked to star formation. Aims. In this work we study cold neutral gas, its H2 component at different epochs, and corresponding depletion times. Methods. We perform state-of-the-art hydrodynamic simulations that include time-dependent atomic and molecular non-equilibrium chemistry coupled to star formation, feedback effects, different UV backgrounds presented in the recent literature and a number of additional processes occurring during structure formation (COLDSIM). We predict gas evolution and contrast the mass density parameters and gas depletion timescales. We also investigate their relation to cosmic expansion in light of the latest infrared and (sub)millimetre observations in the redshift range 2 ≲ z ≲ 7. Results. By performing updated non-equilibrium chemistry calculations we are able to broadly reproduce the latest HI and H2 observations. We find neutral-gas mass density parameters Ωneutral ≃ 10−3 and increasing from lower to higher redshift, in agreement with available HI data. Because of the typically low metallicities during the epoch of reionisation, time-dependent H2 formation is mainly led by the H− channel in self-shielded gas, while H2 grain catalysis becomes important in locally enriched sites at any redshift. Ultraviolet (UV) radiation provides free electrons and facilitates H2 build-up while heating cold metal-poor environments. Resulting H2 fractions can be as high as ∼50% of the cold gas mass at z ∼ 4–8, in line with the latest measurements from high-redshift galaxies. The H2 mass density parameter increases with time until a plateau of ΩH2 ≃ 10−4 is reached. Quantitatively, we find agreement between the derived ΩH2 values and the observations up to z ∼ 7 and both HI and H2 trends are better reproduced by our non-equilibrium H2-based star formation modelling. The predicted gas depletion timescales decrease at lower z in the whole time interval considered, with H2 depletion times remaining below the Hubble time and comparable to the dynamical time at all z. This implies that non-equilibrium molecular cooling is efficient at driving cold-gas collapse in a broad variety of environments and has done so since very early cosmic epochs. While the evolution of chemical species is clearly affected by the details of the UV background and gas self shielding, the assumptions on the adopted initial mass function, different parameterizations of H2 dust grain catalysis, photoelectric heating, and cosmic-ray heating can affect the results in a non-trivial way. In the Appendix, we show detailed analyses of individual processes, as well as simple numerical parameterizations and fits to account for them. Conclusions. Our findings suggest that, in addition to HI, non-equilibrium H2 observations are pivotal probes for assessing cold-gas cosmic abundances and the role of UV background radiation at different epochs.

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Section: Discussionmentioning

confidence: 99%

Atomic and molecular gas from the epoch of reionisation down to redshift 2

Maio

Péroux

Ciardi

2022

A&A

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“…Similarly, although the intensity of the LW background produced by stellar sources and accreting black holes increases very rapidly in the biased region where the bright quasar and its host galaxy are assembling (see Fig. 5 of Valiante et al 2016b), local fluctuations of the LW intensity from nearby sources can significantly exceed the background level, suppressing H 2 cooling and aiding to win the competition between LW radiation and metal winds in heavy seeds hosts (Ahn et al 2009;Regan et al 2014;Dijkstra et al 2014;Inayoshi & Tanaka 2015;Habouzit et al 2016a;Agarwal et al 2017;Maio et al 2019;Mayer & Bonoli 2019).…”

Section: Inhomogeneous Feedbackmentioning

confidence: 99%

“…In fact, in the redshift range where BH seeds are expected to form, the mean LW background is significantly smaller than the required critical value above which H 2 cooling in atomic cooling halos is suppressed, unless the region under investigation is particularly over-dense (Valiante et al 2016a,b). Hence, heavy seeds form when their potential host halo is illuminated by a super-critical J LW from a nearby galaxy (Visbal et al 2014;Habouzit et al 2016b;Regan et al 2019;Maio et al 2019), whose distance must not be too close in order to avoid gas stripping or tidal distortions, which would prevent the formation of the SMS (Chon et al 2016). This motivates the importance of considering the nonlinear spatial distribution of the UV emitting sources around a certain atomic cooling halo, M 1 , candidate to host a heavy or medium-weight seed.…”

Section: Inhomogeneous J Lw Fluxmentioning

confidence: 99%

“…An alternative scenario to grow SMBHs in the early Universe is to start from heavy seeds, ∼ 10 5 M BHs formed from the collapse of supermassive stars (SMSs) (Omukai 2001;Bromm & Loeb 2003;Wise et al 2008;Regan & Haehnelt 2009;Shang et al 2010;Hosokawa et al 2012;Latif et al 2013;Inayoshi et al 2014;Regan et al 2014;Becerra et al 2015;Chon et al 2016;Latif et al 2016;Becerra et al 2018;Wise et al 2019a;Maio et al 2019) or in gas-rich galaxy mergers (Mayer et al 2015;Mayer 2017;Mayer & Bonoli 2019). In the first case, gas cooling and fragmentation must be avoided to form a single supermassive object.…”

Section: Introductionmentioning

confidence: 99%

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Light, medium-weight, or heavy? The nature of the first supermassive black hole seeds

Sassano

Schneider

Valiante

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Observations of hyper-luminous quasars at z > 6 reveal the rapid growth of supermassive black holes (SMBHs $>10^9 \rm M_{\odot }$) whose origin is still difficult to explain. Their progenitors may have formed as remnants of massive, metal free stars (light seeds), via stellar collisions (medium-weight seeds) and/or massive gas clouds direct collapse (heavy seeds). In this work we investigate for the first time the relative role of these three seed populations in the formation of z > 6 SMBHs within an Eddington-limited gas accretion scenario. To this aim, we implement in our semi-analytical data-constrained model a statistical description of the spatial fluctuations of Lyman-Werner (LW) photo-dissociating radiation and of metal/dust enrichment. This allows us to set the physical conditions for BH seeds formation, exploring their relative birth rate in a highly biased region of the Universe at z > 6. We find that the inclusion of medium-weight seeds does not qualitatively change the growth history of the first SMBHs: although less massive seeds ($<10^3 \rm M_\odot$) form at a higher rate, the mass growth of a $\sim 10^9 \rm M_\odot$ SMBH at z < 15 is driven by efficient gas accretion (at a sub-Eddington rate) on to its heavy progenitors ($10^5 \rm M_\odot$). This conclusion holds independently of the critical level of LW radiation and even when medium-weight seeds are allowed to form in higher metallicity galaxies, via the so-called super-competitive accretion scenario. Our study suggests that the genealogy of z ∼ 6 SMBHs is characterized by a rich variety of BH progenitors, which represent only a small fraction ($< 10 - 20{{\ \rm per\ cent}}$) of all the BHs that seed galaxies at z > 15.

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“…Hydrodynamical studies of metal-mixing in halos due to external SNe winds have found, however, that the extent of the impact is often over-estimated in large simulations. In practice, metal-pollution in primordial gas is complicated by a number of considerations, including the rate at which winds expel metals from their original galaxies, the propagation of metals through the Intergalactic medium (IGM), and subsequent mixing in gas of varying density (Cen & Riquelme 2008;Maio et al 2019;Smith et al 2015). Recently, Agarwal et al (2017c) devised a semi-analytical model which explores the worst case scenario for DCBH formation, given metal-pollution driven by the same galaxies which provide the necessary LW flux.…”

Section: Narrowing In On the Number Of Dcbhsmentioning

confidence: 99%

Titans of the early Universe: The Prato statement on the origin of the first supermassive black holes

Woods

Agarwal²,

Bromm

et al. 2019

Publ. Astron. Soc. Aust.

161

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In recent years, the discovery of massive quasars at $z\sim7$ has provided a striking challenge to our understanding of the origin and growth of supermassive black holes in the early Universe. Mounting observational and theoretical evidence indicates the viability of massive seeds, formed by the collapse of supermassive stars, as a progenitor model for such early, massive accreting black holes. Although considerable progress has been made in our theoretical understanding, many questions remain regarding how (and how often) such objects may form, how they live and die, and how next generation observatories may yield new insight into the origin of these primordial titans. This review focusses on our present understanding of this remarkable formation scenario, based on the discussions held at the Monash Prato Centre from November 20 to 24, 2017, during the workshop ‘Titans of the Early Universe: The Origin of the First Supermassive Black Holes’.

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The seeds of supermassive black holes and the role of local radiation and metal spreading

Cited by 21 publications

References 177 publications

Atomic and molecular gas from the epoch of reionisation down to redshift 2

Atomic and molecular gas from the epoch of reionisation down to redshift 2

Light, medium-weight, or heavy? The nature of the first supermassive black hole seeds

Titans of the early Universe: The Prato statement on the origin of the first supermassive black holes

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