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The deepest X-ray view of high-redshift galaxies : Constraints on low-rate black hole accretion

Vito, F. ; Gilli, R. ; Vignali, C. ; Brandt, W. N. ; Comastri, A. ; Yang, G. ; Lehmer, B. D. ; Luo, B. ; Basu-Zych, A. and Bauer, F. E. , et al. (2016) In Monthly Notices of the Royal Astronomical Society 463(1). p.348-374
Abstract

We exploit the 7 Ms Chandra observations in the Chandra Deep Field-South (CDF-S), the deepest X-ray survey to date, coupled with CANDELS/GOODS-S data, to measure the total X-ray emission arising from 2076 galaxies at 3.5 ≤ z < 6.5. This aim is achieved by stacking the Chandra data at the positions of optically selected galaxies, reaching effective exposure times of ≥109s.We detect significant (>3.7s) X-ray emission from massive galaxies at z ≈ 4. We also report the detection of massive galaxies at z ≈ 5 at a 99.7 per cent confidence level (2.7σ), the highest significance ever obtained for X-ray emission from galaxies at such high redshifts. No significant signal is detected from galaxies at even higher redshifts. The... (More)

We exploit the 7 Ms Chandra observations in the Chandra Deep Field-South (CDF-S), the deepest X-ray survey to date, coupled with CANDELS/GOODS-S data, to measure the total X-ray emission arising from 2076 galaxies at 3.5 ≤ z < 6.5. This aim is achieved by stacking the Chandra data at the positions of optically selected galaxies, reaching effective exposure times of ≥109s.We detect significant (>3.7s) X-ray emission from massive galaxies at z ≈ 4. We also report the detection of massive galaxies at z ≈ 5 at a 99.7 per cent confidence level (2.7σ), the highest significance ever obtained for X-ray emission from galaxies at such high redshifts. No significant signal is detected from galaxies at even higher redshifts. The stacking results place constraints on theBHADassociated with the known high-redshift galaxy samples, as well as on the SFRD at high redshift, assuming a range of prescriptions for X-ray emission due to X- ray binaries.We find that the X-ray emission from our sample is likely dominated by processes related to star formation. Our results show that low-rate mass accretion on to SMBHs in individually X-ray-undetected galaxies is negligible, compared with the BHAD measured for samples of X-ray detected AGN, for cosmic SMBH mass assembly at high redshift. We also place, for the first time, constraints on the faint-end of the AGN X-ray luminosity function (logLX ~ 42) at z > 4, with evidence for fairly flat slopes. The implications of all of these findings are discussed in the context of the evolution of the AGN population at high redshift.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Galaxies: active, Galaxies: evolution, Galaxies: high, methods: data analysis, Redshift, Surveys, X-rays: galaxies
in
Monthly Notices of the Royal Astronomical Society
volume
463
issue
1
pages
27 pages
publisher
Oxford University Press
external identifiers
  • scopus:85011553917
ISSN
0035-8711
DOI
10.1093/mnras/stw1998
language
English
LU publication?
yes
id
df1a61c3-4f01-4bb6-a070-15085b567d1d
date added to LUP
2022-10-28 12:54:00
date last changed
2024-04-18 15:19:06
@article{df1a61c3-4f01-4bb6-a070-15085b567d1d,
  abstract     = {{<p>We exploit the 7 Ms Chandra observations in the Chandra Deep Field-South (CDF-S), the deepest X-ray survey to date, coupled with CANDELS/GOODS-S data, to measure the total X-ray emission arising from 2076 galaxies at 3.5 ≤ z &lt; 6.5. This aim is achieved by stacking the Chandra data at the positions of optically selected galaxies, reaching effective exposure times of ≥10<sup>9</sup>s.We detect significant (&gt;3.7s) X-ray emission from massive galaxies at z ≈ 4. We also report the detection of massive galaxies at z ≈ 5 at a 99.7 per cent confidence level (2.7σ), the highest significance ever obtained for X-ray emission from galaxies at such high redshifts. No significant signal is detected from galaxies at even higher redshifts. The stacking results place constraints on theBHADassociated with the known high-redshift galaxy samples, as well as on the SFRD at high redshift, assuming a range of prescriptions for X-ray emission due to X- ray binaries.We find that the X-ray emission from our sample is likely dominated by processes related to star formation. Our results show that low-rate mass accretion on to SMBHs in individually X-ray-undetected galaxies is negligible, compared with the BHAD measured for samples of X-ray detected AGN, for cosmic SMBH mass assembly at high redshift. We also place, for the first time, constraints on the faint-end of the AGN X-ray luminosity function (logLX ~ 42) at z &gt; 4, with evidence for fairly flat slopes. The implications of all of these findings are discussed in the context of the evolution of the AGN population at high redshift.</p>}},
  author       = {{Vito, F. and Gilli, R. and Vignali, C. and Brandt, W. N. and Comastri, A. and Yang, G. and Lehmer, B. D. and Luo, B. and Basu-Zych, A. and Bauer, F. E. and Cappelluti, N. and Koekemoer, A. and Mainieri, V. and Paolillo, M. and Ranalli, P. and Shemmer, O. and Trump, J. and Wang, J. X. and Xue, Y. Q.}},
  issn         = {{0035-8711}},
  keywords     = {{Galaxies: active; Galaxies: evolution; Galaxies: high; methods: data analysis; Redshift; Surveys; X-rays: galaxies}},
  language     = {{eng}},
  month        = {{11}},
  number       = {{1}},
  pages        = {{348--374}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{The deepest X-ray view of high-redshift galaxies : Constraints on low-rate black hole accretion}},
  url          = {{http://dx.doi.org/10.1093/mnras/stw1998}},
  doi          = {{10.1093/mnras/stw1998}},
  volume       = {{463}},
  year         = {{2016}},
}