A systematic search for z ≥ 5 active galactic nuclei in the Chandra Deep Field South
Abstract
We investigate early black hole growth through the methodical search for z ≥ 5 AGN in the Chandra Deep Field South.We base our search on the Chandra 4-Ms data that should allow us to detect Compton-thin AGN with MBH >107 M⊙ accreting at Eddington ratios > 0.1.The Chandra Deep Field South contains over 600 z ≥ 5 Lyman Break Galaxies. These high-redshift galaxies are the progenitors of massive, local galaxies and based on lower redshift relations we would expect ~ 20 of them to host AGN.We combine the Chandra data with GOODS/ACS, CANDELS/WFC3 and Spitzer/IRAC data. After excluding clear low-redshift sources our sample consists of 58 high-redshift candidates. We use a range of redshift estimators including a photo-z code, stacking, colour criteria and the Lyman Break Technique. We also use the X-ray Hardness Ratio as additional information.The final z ≥ 5 candidates that remain after we combine our redshift tests, are likely to be low-redshift interlopers. We thus conclude that, contrary to our expectation of finding at least a few high-redshift AGN, the field does not contain any convincing z ≥ 5 AGN candidates.Our results place interesting constraints on early black hole growth and we discuss a range of possible explanations.
- Publication:
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American Astronomical Society Meeting Abstracts #225
- Pub Date:
- January 2015
- Bibcode:
- 2015AAS...22534710W