The University of Southampton
University of Southampton Institutional Repository
Warning ePrints Soton is experiencing an issue with some file downloads not being available. We are working hard to fix this. Please bear with us.

Accretion history of AGNs. III. Radiative efficiency and AGN contribution to reionization

Accretion history of AGNs. III. Radiative efficiency and AGN contribution to reionization
Accretion history of AGNs. III. Radiative efficiency and AGN contribution to reionization
The cosmic history of supermassive black hole (SMBH) growth is important for understanding galaxy evolution, reionization, and the physics of accretion. Recent NuSTAR, Swift-BAT, and Chandra hard X-ray surveys have provided new constraints on the space density of heavily obscured active galactic nuclei (AGNs). Using the new X-ray luminosity function derived from these data, we here estimate the accretion efficiency of SMBHs and their contribution to reionization. We calculate the total ionizing radiation from AGNs as a function of redshift, based on the X radiation and distribution of obscuring column density, converted to ultraviolet (UV) wavelengths. Limiting the luminosity function to unobscured AGNs only, our results agree with current UV luminosity functions of unobscured AGNs. For realistic assumptions about the escape fraction, the contribution of all AGNs to cosmic reionization is ~4 times lower than the galaxy contribution (23% at z ~ 6). Our results also offer an observationally constrained prescription that can be used in simulations or models of galaxy evolution. To estimate the average efficiency with which SMBHs convert mass to light, we compare the total radiated energy, converted from X-ray light using a bolometric correction, with the most recent local black hole mass density. The most likely value, η ~ 0.3–0.34, approaches the theoretical limit for a maximally rotating Kerr black hole, η = 0.42, implying that on average growing SMBHs are spinning rapidly.
0004-637X
Ananna, Tonima T.
d748e8f3-4390-40ab-be63-a5b2a223981b
Megan Urry, C.
c1f9cd35-c309-47e1-95ec-08558d88be08
Treister, Ezequiel
41255c65-540c-43de-ae46-78299b585717
Hickox, Ryan C.
fa3d8d11-419b-4625-892f-7183fba98e8a
Shankar, Francesco
b10c91e4-85cd-4394-a18a-d4f049fd9cdb
Ricci, Claudio
47c48bd5-233e-41dd-824a-3df26357d84f
Cappelluti, Nico
ec0e1455-2f05-48e6-8a71-9b779581ee64
Marchesi, Stefano
82bbf999-4609-4e6a-a7e2-422135c09f51
Turner, Tracey Jane
fb280046-6ff5-4756-a17a-3fc20166d90b
Ananna, Tonima T.
d748e8f3-4390-40ab-be63-a5b2a223981b
Megan Urry, C.
c1f9cd35-c309-47e1-95ec-08558d88be08
Treister, Ezequiel
41255c65-540c-43de-ae46-78299b585717
Hickox, Ryan C.
fa3d8d11-419b-4625-892f-7183fba98e8a
Shankar, Francesco
b10c91e4-85cd-4394-a18a-d4f049fd9cdb
Ricci, Claudio
47c48bd5-233e-41dd-824a-3df26357d84f
Cappelluti, Nico
ec0e1455-2f05-48e6-8a71-9b779581ee64
Marchesi, Stefano
82bbf999-4609-4e6a-a7e2-422135c09f51
Turner, Tracey Jane
fb280046-6ff5-4756-a17a-3fc20166d90b

Ananna, Tonima T., Megan Urry, C., Treister, Ezequiel, Hickox, Ryan C., Shankar, Francesco, Ricci, Claudio, Cappelluti, Nico, Marchesi, Stefano and Turner, Tracey Jane (2020) Accretion history of AGNs. III. Radiative efficiency and AGN contribution to reionization. Astrophysical Journal, 903 (2), [85]. (doi:10.3847/1538-4357/abb815).

Record type: Article

Abstract

The cosmic history of supermassive black hole (SMBH) growth is important for understanding galaxy evolution, reionization, and the physics of accretion. Recent NuSTAR, Swift-BAT, and Chandra hard X-ray surveys have provided new constraints on the space density of heavily obscured active galactic nuclei (AGNs). Using the new X-ray luminosity function derived from these data, we here estimate the accretion efficiency of SMBHs and their contribution to reionization. We calculate the total ionizing radiation from AGNs as a function of redshift, based on the X radiation and distribution of obscuring column density, converted to ultraviolet (UV) wavelengths. Limiting the luminosity function to unobscured AGNs only, our results agree with current UV luminosity functions of unobscured AGNs. For realistic assumptions about the escape fraction, the contribution of all AGNs to cosmic reionization is ~4 times lower than the galaxy contribution (23% at z ~ 6). Our results also offer an observationally constrained prescription that can be used in simulations or models of galaxy evolution. To estimate the average efficiency with which SMBHs convert mass to light, we compare the total radiated energy, converted from X-ray light using a bolometric correction, with the most recent local black hole mass density. The most likely value, η ~ 0.3–0.34, approaches the theoretical limit for a maximally rotating Kerr black hole, η = 0.42, implying that on average growing SMBHs are spinning rapidly.

Text
Accretion history of AGNs. III. Radiative efficiency and AGN contribution to reionization - Accepted Manuscript
Download (845kB)

More information

Accepted/In Press date: 12 September 2020
e-pub ahead of print date: 4 November 2020
Published date: November 2020
Additional Information: arxiv is am

Identifiers

Local EPrints ID: 446248
URI: http://eprints.soton.ac.uk/id/eprint/446248
ISSN: 0004-637X
PURE UUID: 530254d0-2e2a-44fe-9ce0-18819ef90422

Catalogue record

Date deposited: 01 Feb 2021 17:30
Last modified: 26 Nov 2021 05:58

Export record

Altmetrics

Contributors

Author: Tonima T. Ananna
Author: C. Megan Urry
Author: Ezequiel Treister
Author: Ryan C. Hickox
Author: Claudio Ricci
Author: Nico Cappelluti
Author: Stefano Marchesi
Author: Tracey Jane Turner

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×