REVEALING A POPULATION OF HEAVILY OBSCURED ACTIVE GALACTIC NUCLEI AT <i>z</i> ≈ 0.5-1 IN THE CHANDRA DEEP FIELD-SOUTH

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dc.contributor.authorLuo, B.
dc.contributor.authorBrandt, W. N.
dc.contributor.authorXue, Y. Q.
dc.contributor.authorAlexander, D. M.
dc.contributor.authorBrusa, M.
dc.contributor.authorBauer, F. E.
dc.contributor.authorComastri, A.
dc.contributor.authorFabian, A. C.
dc.contributor.authorGilli, R.
dc.contributor.authorLehmer, B. D.
dc.contributor.authorRafferty, D. A.
dc.contributor.authorSchneider, D. P.
dc.contributor.authorVignali, C.
dc.date.accessioned2025-01-21T00:00:37Z
dc.date.available2025-01-21T00:00:37Z
dc.date.issued2011
dc.description.abstractHeavily obscured (NH greater than or similar to 3 x 10(23) cm(-2)) active galactic nuclei (AGNs) not detected even in the deepest X-ray surveys are often considered to be comparably numerous to the unobscured and moderately obscured AGNs. Such sources are required to fit the cosmic X-ray background (XRB) emission in the 10-30 keV band. We identify a numerically significant population of heavily obscured AGNs at z approximate to 0.5-1 in the Chandra Deep Field-South (CDF-S) and Extended Chandra Deep Field-South by selecting 242 X-ray undetected objects with infrared-based star-formation rates (SFRs) substantially higher (a factor of 3.2 or more) than their SFRs determined from the UV after correcting for dust extinction. An X-ray stacking analysis of 23 candidates in the central CDF-S region using the 4 Ms Chandra data reveals a hard X-ray signal with an effective power-law photon index of Gamma = 0.6(-0.4)(+ 0.3), indicating a significant contribution from obscured AGNs. Based on Monte Carlo simulations, we conclude that 74% +/- 25% of the selected galaxies host obscured AGNs, within which approximate to 95% are heavily obscured and approximate to 80% are Compton-thick (CT; N-H > 1.5 x 10(24) cm(-2)). The heavily obscured objects in our sample are of moderate intrinsic X-ray luminosity (approximate to(0.9-4) x 10(42) erg s(-1) in the 2-10 keV band). The space density of the CT AGNs is (1.6 +/- 0.5) x 10(-4) Mpc(-3). The z approximate to 0.5-1 CT objects studied here are expected to contribute approximate to 1% of the total XRB flux in the 10-30 keV band, and they account for approximate to 5%-15% of the emission in this energy band expected from all CT AGNs according to population-synthesis models. In the 6-8 keV band, the stacked signal of the 23 heavily obscured candidates accounts for <5% of the unresolved XRB flux, while the unresolved approximate to 25% of the XRB in this band can probably be explained by a stacking analysis of the X-ray undetected optical galaxies in the CDF-S (a 2.5 sigma stacked signal). We discuss prospects to identify such heavily obscured objects using future hard X-ray observatories.
dc.fuente.origenWOS
dc.identifier.doi10.1088/0004-637X/740/1/37
dc.identifier.eissn1538-4357
dc.identifier.issn0004-637X
dc.identifier.urihttps://doi.org/10.1088/0004-637X/740/1/37
dc.identifier.urihttps://repositorio.uc.cl/handle/11534/95349
dc.identifier.wosidWOS:000295256500037
dc.issue.numero1
dc.language.isoen
dc.revistaAstrophysical journal
dc.rightsacceso restringido
dc.subjectcosmic background radiation
dc.subjectgalaxies: active
dc.subjectgalaxies: photometry
dc.subjectgalaxies: starburst
dc.subjectinfrared: galaxies
dc.subjectX-rays: galaxies
dc.titleREVEALING A POPULATION OF HEAVILY OBSCURED ACTIVE GALACTIC NUCLEI AT <i>z</i> ≈ 0.5-1 IN THE CHANDRA DEEP FIELD-SOUTH
dc.typeartículo
dc.volumen740
sipa.indexWOS
sipa.trazabilidadWOS;2025-01-12
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