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The Search for the Farthest Quasar: Consequences for Black Hole Growth and Seed Models

The Search for the Farthest Quasar: Consequences for Black Hole Growth and Seed Models Abstract The quest for high-redshift quasars has led to a series of record-breaking sources, with the current record holder at z = 7.642. Here, we show how future detections of z > 8 quasars impact the constraints on the parameters for black hole growth and seed models. Using broad flat priors on the growth parameters (Eddington ratio  fEdd, duty cycle |${\cal D}$|⁠, seed mass M•, seed and radiative efficiency ε), we show that the large uncertainties in their determination decrease by a factor ∼5 when a quasar’s detection redshift goes from z = 9 to z = 12. In this high-redshift regime, ε tends to the lowest value allowed, and the distribution for M•, seed peaks well inside the heavy seed domain. Remarkably, two quasars detected at z > 7 with low accretion rates (J1243+0100 and J0313-1806) already tighten the available parameter space, requiring M•, seed > 103.5 M⊙ and ε < 0.1. The radiative efficiency is a crucial unknown, with factor ∼2 changes able to modify the predicted mass by ∼3 orders of magnitude already at z ∼ 9. The competing roles of inefficient accretion (decreasing ε) and black hole spin-up (increasing ε) significantly impact growth models. Finally, we suggest that yields currently predicted by upcoming quasar surveys (e.g., Euclid) will be instrumental for determining the most-likely seed mass regime. For example, assuming thin-disk accretion, a detection of a quasar with M• ∼ 1010 M⊙ by z ∼ 9 − 10 would exclude the entire parameter space available for light seeds and dramatically reduce the one for heavy seeds. black hole physics, methods: statistical, galaxies: active, quasars: general, early Universe, surveys This content is only available as a PDF. © 2021 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Monthly Notices of the Royal Astronomical Society Oxford University Press

The Search for the Farthest Quasar: Consequences for Black Hole Growth and Seed Models

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References (16)

Publisher
Oxford University Press
Copyright
Copyright © 2021 The Royal Astronomical Society
ISSN
0035-8711
eISSN
1365-2966
DOI
10.1093/mnras/stab3071
Publisher site
See Article on Publisher Site

Abstract

Abstract The quest for high-redshift quasars has led to a series of record-breaking sources, with the current record holder at z = 7.642. Here, we show how future detections of z > 8 quasars impact the constraints on the parameters for black hole growth and seed models. Using broad flat priors on the growth parameters (Eddington ratio  fEdd, duty cycle |${\cal D}$|⁠, seed mass M•, seed and radiative efficiency ε), we show that the large uncertainties in their determination decrease by a factor ∼5 when a quasar’s detection redshift goes from z = 9 to z = 12. In this high-redshift regime, ε tends to the lowest value allowed, and the distribution for M•, seed peaks well inside the heavy seed domain. Remarkably, two quasars detected at z > 7 with low accretion rates (J1243+0100 and J0313-1806) already tighten the available parameter space, requiring M•, seed > 103.5 M⊙ and ε < 0.1. The radiative efficiency is a crucial unknown, with factor ∼2 changes able to modify the predicted mass by ∼3 orders of magnitude already at z ∼ 9. The competing roles of inefficient accretion (decreasing ε) and black hole spin-up (increasing ε) significantly impact growth models. Finally, we suggest that yields currently predicted by upcoming quasar surveys (e.g., Euclid) will be instrumental for determining the most-likely seed mass regime. For example, assuming thin-disk accretion, a detection of a quasar with M• ∼ 1010 M⊙ by z ∼ 9 − 10 would exclude the entire parameter space available for light seeds and dramatically reduce the one for heavy seeds. black hole physics, methods: statistical, galaxies: active, quasars: general, early Universe, surveys This content is only available as a PDF. © 2021 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Journal

Monthly Notices of the Royal Astronomical Society – Oxford University Press

Published: Oct 22, 2021

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