Direct collapse black holes (BHs) are promising candidates for producing massive z ≳ 6 quasars, but their formation requires finetuned conditions. In this work, we use cosmological zoom simulations to study systematically the impact of requiring: (1) low gas angular momentum (spin), and (2) a minimum incident Lyman–Werner (LW) flux in order to form BH seeds. We probe the formation of seeds (with initial masses of $M_{\rm seed} \sim 10^4\!\!10^6\, \mathrm{M}_{\odot }\, h^{1})$ in haloes with a total mass >3000 × Mseed and a dense, metalpoor gas mass >5 × Mseed. Within this framework, we find that the seedforming haloes have a prior history of star formation and metal enrichment, but they also contain pockets of dense, metalpoor gas. When seeding is further restricted to haloes with low gas spins, the number of seeds formed is suppressed by factors of ∼6 compared to the baseline model, regardless of the seed mass. Seed formation is much more strongly impacted if the dense, metalpoor gas is required to have a critical LW flux (Jcrit). Even for Jcrit values as low as 50J21, no $8\times 10^{5}~\mathrm{M}_{\odot }\, h^{1}$ seeds are formed. While lower mass ($1.25\times 10^{4},1\times 10^{5}~\mathrm{M}_{\odot }\, h^{1}$) seeds do form, they are strongly suppressed (by factors of ∼10–100) comparedmore »
We explore implications of a range of black hole (BH) seeding prescriptions on the formation of the brightest $z$ ≳ 6 quasars in cosmological hydrodynamic simulations. The underlying galaxy formation model is the same as in the IllustrisTNG simulations. Using constrained initial conditions, we study the growth of BHs in rare overdense regions (forming $\gtrsim 10^{12}\, {\rm M}_{\odot }\,h^{1}$ haloes by $z$ = 7) using a (9 Mpc h−1)3 simulated volume. BH growth is maximal within haloes that are compact and have a low tidal field. For these haloes, we consider an array of gasbased seeding prescriptions wherein $M_{\mathrm{seed}}=10^4\!\!10^6\, {\rm M}_{\odot }\,h^{1}$ seeds are inserted in haloes above critical thresholds for halo mass and dense, metalpoor gas mass (defined as $\tilde{M}_{\mathrm{h}}$ and $\tilde{M}_{\mathrm{sf,mp}}$, respectively, in units of Mseed). We find that a seed model with $\tilde{M}_{\mathrm{sf,mp}}=5$ and $\tilde{M}_{\mathrm{h}}=3000$ successfully produces a $z$ ∼ 6 quasar with $\sim 10^9\, {\rm M}_{\odot }$ mass and ∼1047 erg s−1 luminosity. BH mergers play a crucial role at $z$ ≳ 9, causing an early boost in BH mass at a time when accretiondriven BH growth is negligible. With more stringent seeding conditions (e.g. $\tilde{M}_{\mathrm{sf,mp}}=1000$), the relative paucity of BH seeds results in a much lower merger rate. In this case, $z$ more »
 Award ID(s):
 1909933
 Publication Date:
 NSFPAR ID:
 10370035
 Journal Name:
 Monthly Notices of the Royal Astronomical Society
 Volume:
 516
 Issue:
 1
 Page Range or eLocationID:
 p. 138157
 ISSN:
 00358711
 Publisher:
 Oxford University Press
 Sponsoring Org:
 National Science Foundation
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