Growth of high redshift supermassive black holes from heavy seeds in the BRAHMA cosmological simulations: Implications of overmassive black holes
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| Format: | Preprint |
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2024
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| _version_ | 1866913399451942912 |
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| author | Bhowmick, Aklant K Blecha, Laura Torrey, Paul Somerville, Rachel S Kelley, Luke Zoltan Vogelsberger, Mark Weinberger, Rainer Hernquist, Lars Sivasankaran, Aneesh |
| author_facet | Bhowmick, Aklant K Blecha, Laura Torrey, Paul Somerville, Rachel S Kelley, Luke Zoltan Vogelsberger, Mark Weinberger, Rainer Hernquist, Lars Sivasankaran, Aneesh |
| contents | JWST has recently revealed a large population of accreting black holes (BHs) in the early Universe. Even after accounting for possible systematic biases, the high-z $M_*-M_{\rm \rm bh}$ relation derived from these objects by Pacucci et al. (2023 P23 relation) is above the local scaling relation by $>3σ$. To understand the implications of potentially overmassive high-z BH populations, we study the BH growth at $z\sim4-7$ using the $[18~\mathrm{Mpc}]^3$ BRAHMA suite of cosmological simulations with systematic variations of heavy seed models that emulate direct collapse black hole (DCBH) formation. In our least restrictive seed model, we place $\sim10^5~M_{\odot}$ seeds in halos with sufficient dense and metal-poor gas. To model conditions for direct collapse, we impose additional criteria based on a minimum Lyman Werner flux (LW flux $=10~J_{21}$), maximum gas spin, and an environmental richness criterion. The high-z BH growth in our simulations is merger dominated, with a relatively small contribution from gas accretion. For the most restrictive simulation that includes all the above seeding criteria for DCBH formation, the high-z $M_*-M_{\rm bh}$ relation falls significantly below the P23 relation (by factor of $\sim10$ at $z\sim4$). Only by excluding the spin and environment based criteria, and by assuming $\lesssim750~\mathrm{Myr}$ delay times between host galaxy mergers and subsequent BH mergers, are we able to reproduce the P23 relation. Overall, our results suggest that if high-z BHs are indeed systematically overmassive, assembling them would require more efficient heavy seeding channels, higher initial seed masses, additional contributions from lighter seeds to BH mergers, and / or more efficient modes for BH accretion. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2406_14658 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Growth of high redshift supermassive black holes from heavy seeds in the BRAHMA cosmological simulations: Implications of overmassive black holes Bhowmick, Aklant K Blecha, Laura Torrey, Paul Somerville, Rachel S Kelley, Luke Zoltan Vogelsberger, Mark Weinberger, Rainer Hernquist, Lars Sivasankaran, Aneesh Astrophysics of Galaxies JWST has recently revealed a large population of accreting black holes (BHs) in the early Universe. Even after accounting for possible systematic biases, the high-z $M_*-M_{\rm \rm bh}$ relation derived from these objects by Pacucci et al. (2023 P23 relation) is above the local scaling relation by $>3σ$. To understand the implications of potentially overmassive high-z BH populations, we study the BH growth at $z\sim4-7$ using the $[18~\mathrm{Mpc}]^3$ BRAHMA suite of cosmological simulations with systematic variations of heavy seed models that emulate direct collapse black hole (DCBH) formation. In our least restrictive seed model, we place $\sim10^5~M_{\odot}$ seeds in halos with sufficient dense and metal-poor gas. To model conditions for direct collapse, we impose additional criteria based on a minimum Lyman Werner flux (LW flux $=10~J_{21}$), maximum gas spin, and an environmental richness criterion. The high-z BH growth in our simulations is merger dominated, with a relatively small contribution from gas accretion. For the most restrictive simulation that includes all the above seeding criteria for DCBH formation, the high-z $M_*-M_{\rm bh}$ relation falls significantly below the P23 relation (by factor of $\sim10$ at $z\sim4$). Only by excluding the spin and environment based criteria, and by assuming $\lesssim750~\mathrm{Myr}$ delay times between host galaxy mergers and subsequent BH mergers, are we able to reproduce the P23 relation. Overall, our results suggest that if high-z BHs are indeed systematically overmassive, assembling them would require more efficient heavy seeding channels, higher initial seed masses, additional contributions from lighter seeds to BH mergers, and / or more efficient modes for BH accretion. |
| title | Growth of high redshift supermassive black holes from heavy seeds in the BRAHMA cosmological simulations: Implications of overmassive black holes |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2406.14658 |