Ab Initio Cosmological Simulations of CR7 as an Active Black Hole

Abstract

We present the first ab initio cosmological simulations of a CR7-like object which approximately reproduce the observed line widths and strengths. In our model, CR7 is powered by a massive ($3.23\times 10^7$ $M_{\odot }$) black hole (BH) the accretion rate of which varies between $\simeq$ 0.25 and $\simeq$ 0.9 times the Eddington rate on timescales as short as 10${}^3$ yr. Our model takes into account multi-dimensional effects, X-ray feedback, secondary ionizations and primordial chemistry. We estimate Ly-$\alpha$ line widths by post-processing simulation output with Monte Carlo radiative transfer and calculate emissivity contributions from radiative recombination and collisional excitation. We find the luminosities in the Lyman-$\alpha$ and He II 1640 angstrom lines to be $5.0\times 10^{44}$ and $2.4\times 10^{43}$ erg s${}^{-1}$, respectively, in agreement with the observed values of $>$ $8.3\times 10^{43}$ and $2.0\times 10^{43}$ erg s${}^{-1}$. We also find that the black hole heats the halo and renders it unable to produce stars as required to keep the halo metal free. These results demonstrate the viability of the BH hypothesis for CR7 in a cosmological context. Assuming the BH mass and accretion rate that we find, we estimate the synchrotron luminosity of CR7 to be $P\simeq 10^{40}-10^{41}$ erg s${}^{-1}$, which is sufficiently luminous to be observed in $\mu$Jy observations and would discriminate this scenario from one where the luminosity is driven by Population III stars.

5 pages, 4 figures, Accepted by ApJ Letters

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• Observational Signatures of High-Redshift Quasars and Local Relics of Black Hole Seeds
• No evidence for Population III stars or a Direct Collapse Black Hole in the z = 6.6 Lyman-$\alpha$ emitter 'CR7'
• Radiation Hydrodynamical Simulations of the First Quasars
• Lyman-alpha radiation hydrodynamics of galactic winds before cosmic reionization
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• Chasing the observational signatures of seed black holes at z > 7: candidate observability
• The nature of the Lyman Alpha Emitter CR7: a persisting puzzle
• The first supermassive black holes
• Radiative effects during the assembly of direct collapse black holes
• Boosting Lya and HeII 1640A Line Fluxes from Pop III Galaxies: Stochastic IMF Sampling and Departures from Case-B
• The Location and Environments of Neutron Star Mergers in an Evolving Universe
• Metallicity evolution of direct collapse black hole hosts: CR7 as a case study
• Enhanced direct collapse due to Lyman alpha feedback
• Triggering the formation of direct collapse black holes by their congeners
• Growth problems of stellar black holes in early galaxies