A. Del Moro
Mid-infrared luminous quasars in the GOODS–Herschel fields: a large population of heavily obscured, Compton-thick quasars at z ≈ 2
Del Moro, A.; Alexander, D.M.; Bauer, F.E.; Daddi, E.; Kocevski, D.D.; McIntosh, D.H.; Stanley, F.; Brandt, W.N.; Elbaz, D.; Harrison, C.M.; Luo, B.; Mullaney, J.R.; Xue, Y.Q.
Authors
Professor David Alexander d.m.alexander@durham.ac.uk
Professor
F.E. Bauer
E. Daddi
D.D. Kocevski
D.H. McIntosh
F. Stanley
W.N. Brandt
D. Elbaz
C.M. Harrison
B. Luo
J.R. Mullaney
Y.Q. Xue
Abstract
We present the infrared (IR) and X-ray properties of a sample of 33 mid-IR luminous quasars (νL6 μm ≥ 6 × 1044 erg s−1) at redshift z ≈ 1–3, identified through detailed spectral energy distribution analyses of distant star-forming galaxies, using the deepest IR data from Spitzer and Herschel in the GOODS–Herschel fields. The aim is to constrain the fraction of obscured, and Compton-thick (CT, NH > 1.5 × 1024 cm−2) quasars at the peak era of nuclear and star formation activities. Despite being very bright in the mid-IR band, ≈30 per cent of these quasars are not detected in the extremely deep 2 and 4 Ms Chandra X-ray data available in these fields. X-ray spectral analysis of the detected sources reveals that the majority (≈67 per cent) are obscured by column densities NH > 1022 cm−2; this fraction reaches ≈80 per cent when including the X-ray-undetected sources (9 out of 33), which are likely to be the most heavily obscured, CT quasars. We constrain the fraction of CT quasars in our sample to be ≈24–48 per cent, and their space density to be Φ = (6.7 ± 2.2) × 10−6 Mpc−3. From the investigation of the quasar host galaxies in terms of star formation rates (SFRs) and morphological distortions, as a sign of galaxy mergers/interactions, we do not find any direct relation between SFRs and quasar luminosity or X-ray obscuration. On the other hand, there is tentative evidence that the most heavily obscured quasars have, on average, more disturbed morphologies than the unobscured/moderately obscured quasar hosts, which preferentially live in undisturbed systems. However, the fraction of quasars with disturbed morphology amongst the whole sample is ≈40 per cent, suggesting that galaxy mergers are not the main fuelling mechanism of quasars at z ≈ 2.
Citation
Del Moro, A., Alexander, D., Bauer, F., Daddi, E., Kocevski, D., McIntosh, D., …Xue, Y. (2016). Mid-infrared luminous quasars in the GOODS–Herschel fields: a large population of heavily obscured, Compton-thick quasars at z ≈ 2. Monthly Notices of the Royal Astronomical Society, 456(2), 2105-2125. https://doi.org/10.1093/mnras/stv2748
Journal Article Type | Article |
---|---|
Acceptance Date | Nov 19, 2015 |
Online Publication Date | Dec 30, 2015 |
Publication Date | Feb 21, 2016 |
Deposit Date | May 31, 2016 |
Publicly Available Date | Mar 29, 2024 |
Journal | Monthly Notices of the Royal Astronomical Society |
Print ISSN | 0035-8711 |
Electronic ISSN | 1365-2966 |
Publisher | Royal Astronomical Society |
Peer Reviewed | Peer Reviewed |
Volume | 456 |
Issue | 2 |
Pages | 2105-2125 |
DOI | https://doi.org/10.1093/mnras/stv2748 |
Related Public URLs | http://adsabs.harvard.edu/abs/2016MNRAS.456.2105D |
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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
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