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The systematic search for z5 active galactic nuclei in the Chandra Deep Field South

The systematic search for z5 active galactic nuclei in the Chandra Deep Field South We investigate early black hole (BH) growth through the methodical search for z5 active galactic nuclei (AGN) in the Chandra Deep Field South. We base our search on the Chandra 4-Ms data with flux limits of 9.11018 (soft, 0.52keV) and 5.51017ergs1cm2 (hard, 28keV). At z5, this corresponds to luminosities as low as 1042 (1043) ergs1 in the soft (hard) band and should allow us to detect Compton-thin AGN with MBH>107M and Eddington ratios >0.1. Our field (0.03deg2) contains over 600z5 Lyman Break Galaxies. Based on lower redshift relations, we would expect 20 of them to host AGN. After combining the Chandra data with Great Observatories Origins Deep Survey (GOODS)/Advanced Camera for Surveys (ACS), CANDELS/Wide Field Camera 3 and Spitzer/Infrared Array Camera data, the sample consists of 58 high-redshift candidates. We run a photometric redshift code, stack the GOODS/ACS data, apply colour criteria and the Lyman Break Technique and use the X-ray Hardness Ratio. We combine our tests and using additional data find that all sources are most likely at low redshift. We also find five X-ray sources without a counterpart in the optical or infrared which might be spurious detections. We conclude that our field does not contain any convincing z5 AGN. Explanations for this result include a low BH occupation fraction, a low AGN fraction, short, super-Eddington growth modes, BH growth through BHBH mergers or in optically faint galaxies. By searching for z5 AGN, we are setting the foundation for constraining early BH growth and seed formation scenarios. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Monthly Notices of the Royal Astronomical Society Oxford University Press

The systematic search for z5 active galactic nuclei in the Chandra Deep Field South

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References (86)

Publisher
Oxford University Press
Copyright
2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
ISSN
0035-8711
eISSN
1365-2966
DOI
10.1093/mnras/stv184
Publisher site
See Article on Publisher Site

Abstract

We investigate early black hole (BH) growth through the methodical search for z5 active galactic nuclei (AGN) in the Chandra Deep Field South. We base our search on the Chandra 4-Ms data with flux limits of 9.11018 (soft, 0.52keV) and 5.51017ergs1cm2 (hard, 28keV). At z5, this corresponds to luminosities as low as 1042 (1043) ergs1 in the soft (hard) band and should allow us to detect Compton-thin AGN with MBH>107M and Eddington ratios >0.1. Our field (0.03deg2) contains over 600z5 Lyman Break Galaxies. Based on lower redshift relations, we would expect 20 of them to host AGN. After combining the Chandra data with Great Observatories Origins Deep Survey (GOODS)/Advanced Camera for Surveys (ACS), CANDELS/Wide Field Camera 3 and Spitzer/Infrared Array Camera data, the sample consists of 58 high-redshift candidates. We run a photometric redshift code, stack the GOODS/ACS data, apply colour criteria and the Lyman Break Technique and use the X-ray Hardness Ratio. We combine our tests and using additional data find that all sources are most likely at low redshift. We also find five X-ray sources without a counterpart in the optical or infrared which might be spurious detections. We conclude that our field does not contain any convincing z5 AGN. Explanations for this result include a low BH occupation fraction, a low AGN fraction, short, super-Eddington growth modes, BH growth through BHBH mergers or in optically faint galaxies. By searching for z5 AGN, we are setting the foundation for constraining early BH growth and seed formation scenarios.

Journal

Monthly Notices of the Royal Astronomical Society – Oxford University Press

Published: Mar 10, 2015

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