Issue |
A&A
Volume 676, August 2023
|
|
---|---|---|
Article Number | A115 | |
Number of page(s) | 10 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361/202345911 | |
Published online | 18 August 2023 |
Unraveling the formation histories of the first supermassive black holes with the Square Kilometre Array’s pulsar timing array
1
Département de Physique Théorique, Université de Genève, 24 quai Ernest-Ansermet, 1211 Genève 4, Switzerland
e-mail: hamsa.padmanabhan@unige.ch
2
Astronomy department, Harvard University, 60 Garden Street, Cambridge, MA 02138, USA
e-mail: aloeb@cfa.harvard.edu
Received:
13
January
2023
Accepted:
28
May
2023
Galaxy mergers at high redshifts trigger activity of their central supermassive black holes, eventually also leading to their coalescence as well as a potential source of low-frequency gravitational waves detectable by the Square Kilometre Array’s pulsar timing array (SKA PTA). Two key parameters related to the fueling of black holes are the Eddington ratio of quasar accretion, ηEdd, and the radiative efficiency of the accretion process, ϵ (which affects the so-called active lifetime of the quasar, tQSO). Here, we forecast the regime of detectability of gravitational wave events with SKA PTA. We find the associated binaries to have orbital periods of the order of weeks to years, observable via relativistic Doppler velocity boosting and/or optical variability of their light curves. Combining the SKA regime of detectability with the latest observational constraints on high-redshift black hole mass and luminosity functions, as well as theoretically motivated prescriptions for the merger rates of dark matter halos, we forecast the number of active counterparts of SKA PTA events expected as a function of primary black hole mass at z ≳ 6. We find that the quasar counterpart of the most massive black holes will be uniquely localizable within the SKA PTA error ellipse at z ≳ 6. We also forecast the number of expected counterparts as a function of the quasars’ Eddington ratios and active lifetimes. Our results show that SKA PTA detections can place robust constraints on the seeding and growth mechanisms of the first supermassive black holes.
Key words: galaxies: high-redshift / quasars: supermassive black holes / gravitational waves
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.