Modelling a bright z = 6 galaxy at the faint end of the AGN luminosity function

Abstract

Recent deep surveys have unravelled a population of faint active galactic nuclei (AGN) in the high redshift Universe, leading to various discussions on their nature and their role during the Epoch of Reionization. We use cosmological radiation-hydrodynamics simulations of a bright galaxy at z = 6 ($M_{\star }\gtrsim 10^{10}{M}_{\odot }$) hosting an actively growing super-massive black hole to study the properties of these objects. In particular, we study how the black hole and the galaxy co-evolve and what is the relative contribution of the AGN and of the stellar populations to the luminosity budget of the system. We find that the feedback from the AGN has no strong effect on the properties of the galaxy, and does not increase the total ionizing luminosity of the host. The average escape fraction of our galaxy is around $f_{\mathrm{esc}}\sim 5\%$. While our galaxy would be selected as an AGN in deep X-ray surveys, most of the UV luminosity is originating from stellar populations. This confirms that there is a transition in the galaxy population from star forming galaxies to quasar hosts, with bright Lyman-Break Galaxies (LBGs) with $M_{\mathrm{UV}}$ around -22 falling in the overlap region. Our results also suggest that faint AGN do not contribute significantly to reionizing the Universe.

10+1 pages, 10+1 figures. Accepted for publications in MNRAS. Key figures: 5 and 10

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Cited by in corpus (14)

• Introducing the THESAN project: radiation-magnetohydrodynamic simulations of the epoch of reionization
• The THESAN project: properties of the intergalactic medium and its connection to Reionization-era galaxies
• The ALMA REBELS Survey. Epoch of Reionization giants: properties of dusty galaxies at $z\approx 7$
• The ionising photon production efficiency at z~6 for Lyman-alpha emitters using JEMS and MUSE
• Host galaxies of high-redshift quasars: supermassive black hole growth and feedback
• Astraeus VI: Hierarchical assembly of AGN and their large-scale effect during the Epoch of Reionization
• Massive black holes in high-redshift Lyman Break Galaxies
• Cosmic reflections I: the structural diversity of simulated and observed low-mass galaxy analogues
• The quasar luminosity function at $z\sim 5$ via deep learning and Bayesian information criterion
• Stirring the cosmic pot: how black hole feedback shapes the matter power spectrum in the Fable simulations
• Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). XIV. A Candidate Type-II Quasar at z=6.1292
• Reionization in HESTIA: Studying reionization in the LG through zoom simulations
• The impact of black hole feedback on the UV luminosity and stellar mass assembly of high-redshift galaxies
• Unveiling an old disk around a massive young leaking blueberry in SDSS-IV MaNGA