Supermassive black hole formation by direct collapse: keeping protogalactic gas H2 free in dark matter haloes with virial temperatures Tvir > rsim 104 K

By Cien Shang, Greg L. Bryan, Zoltán Haiman. 2009

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In the absence of H 2 molecules, the primordial gas in early dark matter haloes with virial temperatures just above T vir ≳ 10 4 K cools by collisional excitation of atomic H. Although it cools efficiently, this gas remains relatively hot, at a temperature near T ∼ 8000 K, and consequently might be able to avoid fragmentation and collapse directly into a supermassive black hole. In order for H 2 formation and cooling to be strongly suppressed, the gas must be irradiated by a sufficiently intense ultraviolet (UV) flux. We performed a suite of three-dimensional hydrodynamical adaptive mesh refinement (AMR) simulations of gas collapse in three different protogalactic haloes with T vir ≳ 10 4 K, irradiated by a UV flux with various intensities and spectra. We determined the critical specific intensity, J crit 21 , required to suppress H 2 cooling in each of the three haloes. For a hard spectrum representative of metal-free stars, we find (in units of 10 ―21 erg s ―1 Hz ―1 sr ―1 cm ―2 ) 10 4 < J crit 21 < 10 5 , while for a softer spectrum, which is characteristic of a normal stellar population, and for which H ― dissociation is important, we find 30 < J crit 21 < 300. These values are a factor of 3-10 lower than previous estimates. We attribute the difference to the higher, more accurate H 2 collisional dissociation rate we adopted. The reduction in J crit 21 exponentially increases the number of rare haloes exposed to supercritical radiation. When H 2 cooling is suppressed, gas collapse starts with a delay, but it ultimately proceeds more rapidly. The infall velocity is near the increased sound speed, and an object as massive as M ∼ 10 5 M ⊙ may form at the centre of these haloes, compared to the M ∼ 10 2 M ⊙ stars forming when H 2 cooling is efficient.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/70188888f18ffb376984d592a7f3625e2cde1475

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Citations in the corpus

Formation of Supermassive Black Hole Seeds (2016, methodology): “The previous studies used idealised spectra to compute the Jcrit21 and found that J crit 21 = 30− 1200 for Trad = 10 4 K and Jcrit21 = 1000 for Trad = 10 5 K (Omukai 2001; Shang et al. 2010; Van Borm & Spaans 2013; Latif et al. 2014c; Johnson et al. 2014).”
Titans of the early Universe: The Prato statement on the origin of the first supermassive black holes (2018, methodology): “…disks (Begelman et al. 2006; Lodato & Natarajan 2006, 2007), (ii) the collapse of a primordial atomiccooling halo into a DCBH (Bromm & Loeb 2003; Shang et al. 2010; Johnson et al. 2012), or (iii) the formation of a very massive star from runaway stellar mergers in a dense cluster (Omukai,…”
FORMATION OF PRIMORDIAL SUPERMASSIVE STARS BY RAPID MASS ACCRETION (2013, background): “…preventing H2 formation have been proposed, e.g., photodissociation by strong UV background (Omukai 2001; Oh & Haiman 2002; Wise et al. 2008; Shang et al. 2010; Wolcott-Green et al. 2011; Inayoshi & Omukai 2011; Agarwal et al. 2012), and collisional dissociation in dense shocks (Inayoshi &…”
Photodissociation of H2 in protogalaxies: modelling self‐shielding in three‐dimensional simulations (2011, background): “…2008a,b; Greif et al. 2010), relied upon estimating NH2 from local properties of the gas (Bromm & Loeb 2003; Johnson et al. 2008; Gnedin et al. 2009; Shang et al. 2010; Johnson et al. 2011), or sacrificed angular resolution, finding the exact column density in a small number of directions to…”
Black hole formation in the early Universe (2013, background): “We also note that for a radiation temperature of 105 K, H2 is mainly dissociated by the Solomon process while for the stellar spectrum of 104 K the main dissociation route is H− (Shang et al. 2010; Wolcott-Green et al. 2011).”
SUPER-CRITICAL GROWTH OF MASSIVE BLACK HOLES FROM STELLAR-MASS SEEDS (2014, background): “Contrary to the formation of MBH seeds by rapid “direct collapse”, this gas supply is not limited by the Kelvin-Helmholtz contraction timescale of the central supermassive proto-star (see, e.g., Shang et al. 2010), but can add to the central black hole mass over the accretion timescale (eq.”
Modeling the Radio Background from the First Black Holes at Cosmic Dawn: Implications for the 21 cm Absorption Amplitude (2018, background): “These seeds can arise from “direct collapse black holes” (DCBHs; Bromm & Loeb 2003; Shang et al. 2010; Johnson et al. 2012), self-gravitating pre-galactic disks (Begelman et al. 2006; Lodato & Natarajan 2006), or runaway stellar mergers (Devecchi & Volonteri 2009; Davies et al. 2011; Stone et al.…”
What drives the growth of black holes (2011, background): “Detailed hydrodynamic simulations have explored this process (e.g., Wise et al., 2008; Regan & Haehnelt, 2009; Shang et al., 2010; Johnson et al., 2011) and indicate that supermassive stars at the centers of halos can, in principle, accrete up to a few ×105 M over ∼2 Myr (Johnson et al., 2011).”
The First Billion Years project: the impact of stellar radiation on the co-evolution of Populations II and III (2012, methodology): “Also following the formulae from Shang et al. (2010), we have for the photodetachment rate of H−, for which we neglect shielding due to its low abundance, kHM,ion,local = (15) 1.5× 10−10 s−1 ( m∗ 103 M⊙ ) × [ N ∗,III ∑ i=1 ( ri 1 kpc )−2 + 4× 103 N ∗,II ∑ i=1 ( ri 1 kpc )−2 ] .”
Ubiquitous seeding of supermassive black holes by direct collapse (2012, background): “…in units of 10−21 erg s−1cm−2Hz−1sr−1) and depends on the stellar density at a given redshift (Greif & Bromm 2006), whereas the critical value,Jcrit, required for direct collapse is ∼ 30 (from Pop II) and∼ 1000 (from Pop III) (Shang et al. 2010; Wolcott-Green et al. 2011, CS10 and WG11 herafter).”