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Lookup NU author(s): Sean Dougherty, Dr Christopher HarrisonORCiD, Dr David Rosario
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2023 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. Observations of the nearby universe reveal an increasing fraction of active galactic nuclei (AGNs) with decreasing projected separation for close galaxy pairs, relative to control galaxies. This implies galaxy interactions play a role in enhancing AGN activity. However, the picture at higher redshift is less established, partly due to limited spectroscopic redshifts. We combine spectroscopic surveys with photometric redshift probability distribution functions for galaxies in the CANDELS and COSMOS surveys, to produce the largest ever sample of galaxy pairs used in an AGN fraction calculation for cosmic noon (0.5 < z < 3). We present a new technique for assessing galaxy pair probability (based on line-of-sight velocities ±1000 km s-1) from photometric redshift posterior convolutions and use these to produce weighted AGN fractions. Over projected separations 5-100 kpc, we find no evidence for enhancement, relative to isolated control galaxies, of X-ray (LX > 1042 erg s-1) or infrared-selected AGN in major (mass ratios up to 4:1) or minor (4:1 to 10:1) galaxy pairs. However, defining the most obscured AGN as those detected in the infrared but not in X-rays, we observe a trend of increasing obscured AGN enhancement at decreasing separations. The peak enhancement, relative to isolated controls, is a factor of 2.08 ± 0.61 for separations <25 kpc. Our simulations with mock data, indicates this could be a lower limit of the true enhancement. If confirmed with improved infrared imaging (e.g. with JWST) and redshifts (e.g. with forthcoming multi-object spectrograph surveys), this would suggest that galaxy interactions play a role in enhancing the most obscured black hole growth at cosmic noon.
Author(s): Dougherty SL, Harrison CM, Kocevski DD, Rosario DJ
Publication type: Article
Publication status: Published
Journal: Monthly Notices of the Royal Astronomical Society
Year: 2024
Volume: 527
Issue: 2
Pages: 3146-3163
Print publication date: 01/01/2024
Online publication date: 08/05/2023
Acceptance date: 27/04/2023
Date deposited: 15/08/2024
ISSN (print): 0035-8711
ISSN (electronic): 1365-2966
Publisher: Oxford University Press
URL: https://doi.org/10.1093/mnras/stad1300
DOI: 10.1093/mnras/stad1300
Data Access Statement: All photometric data, redshift information, and derived quantities (e.g. stellar masses) used in this work are available in public catalogues as described in Section 3. The derived values of this work, presented in Figs 6–9, are tabulated in Appendix D. Code used in this work is available on github (https://github.com/sldough21/pair-convolutions).
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