Why optically faint AGNs are optically faint: The spitzer perspective

J. R. Rigby; G. H. Rieke; P. G. Pérez-González; J. L. Donley; A. Alonso-Herrero; J. S. Huang; P. Barmby; G. G. Fazio

doi:10.1086/430398

Why optically faint AGNs are optically faint: The spitzer perspective

J. R. Rigby, G. H. Rieke, P. G. Pérez-González, J. L. Donley, A. Alonso-Herrero, J. S. Huang, P. Barmby, G. G. Fazio

Research output: Contribution to journal › Review article › peer-review

19 Scopus citations

Abstract

Optically faint X-ray sources (those f_X/f_R > 10) constitute about 20% of X-ray sources in deep surveys and are potentially highly obscured and/or at high redshift. Their faint optical fluxes are generally beyond the reach of spectroscopy. For a sample of 20 optically faint sources in CDFS, we compile 0.4-24 μm photometry, relying heavily on the Spitzer Space Telescope. We estimate photometric redshifts for 17 of these 20 sources. We find that these AGNs are optically faint, both because they lie at significantly higher redshifts (median z ∼ 1.6) than most X-ray-selected AGNs, and because their spectra are much redder than standard AGNs. They have 2-8 keV X-ray luminosities in the Seyfert range, unlike the QSO luminosities of optically faint AGNs found in shallow wide-field surveys. Their contribution to the X-ray Seyfert luminosity function is comparable to that of z > 1 optically bright AGNs.

Original language	English (US)
Pages (from-to)	134-139
Number of pages	6
Journal	Astrophysical Journal
Volume	627
Issue number	1 I
DOIs	https://doi.org/10.1086/430398
State	Published - Jul 1 2005

Keywords

Galaxies: active
Infrared: galaxies
X-rays: galaxies

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1086/430398

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title = "Why optically faint AGNs are optically faint: The spitzer perspective",

abstract = "Optically faint X-ray sources (those fX/fR > 10) constitute about 20% of X-ray sources in deep surveys and are potentially highly obscured and/or at high redshift. Their faint optical fluxes are generally beyond the reach of spectroscopy. For a sample of 20 optically faint sources in CDFS, we compile 0.4-24 μm photometry, relying heavily on the Spitzer Space Telescope. We estimate photometric redshifts for 17 of these 20 sources. We find that these AGNs are optically faint, both because they lie at significantly higher redshifts (median z ∼ 1.6) than most X-ray-selected AGNs, and because their spectra are much redder than standard AGNs. They have 2-8 keV X-ray luminosities in the Seyfert range, unlike the QSO luminosities of optically faint AGNs found in shallow wide-field surveys. Their contribution to the X-ray Seyfert luminosity function is comparable to that of z > 1 optically bright AGNs.",

keywords = "Galaxies: active, Infrared: galaxies, X-rays: galaxies",

author = "Rigby, {J. R.} and Rieke, {G. H.} and P{\'e}rez-Gonz{\'a}lez, {P. G.} and Donley, {J. L.} and A. Alonso-Herrero and Huang, {J. S.} and P. Barmby and Fazio, {G. G.}",

year = "2005",

month = jul,

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doi = "10.1086/430398",

language = "English (US)",

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journal = "Astrophysical Journal",

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TY - JOUR

T1 - Why optically faint AGNs are optically faint

T2 - The spitzer perspective

AU - Rigby, J. R.

AU - Rieke, G. H.

AU - Pérez-González, P. G.

AU - Donley, J. L.

AU - Alonso-Herrero, A.

AU - Huang, J. S.

AU - Barmby, P.

AU - Fazio, G. G.

PY - 2005/7/1

Y1 - 2005/7/1

N2 - Optically faint X-ray sources (those fX/fR > 10) constitute about 20% of X-ray sources in deep surveys and are potentially highly obscured and/or at high redshift. Their faint optical fluxes are generally beyond the reach of spectroscopy. For a sample of 20 optically faint sources in CDFS, we compile 0.4-24 μm photometry, relying heavily on the Spitzer Space Telescope. We estimate photometric redshifts for 17 of these 20 sources. We find that these AGNs are optically faint, both because they lie at significantly higher redshifts (median z ∼ 1.6) than most X-ray-selected AGNs, and because their spectra are much redder than standard AGNs. They have 2-8 keV X-ray luminosities in the Seyfert range, unlike the QSO luminosities of optically faint AGNs found in shallow wide-field surveys. Their contribution to the X-ray Seyfert luminosity function is comparable to that of z > 1 optically bright AGNs.

AB - Optically faint X-ray sources (those fX/fR > 10) constitute about 20% of X-ray sources in deep surveys and are potentially highly obscured and/or at high redshift. Their faint optical fluxes are generally beyond the reach of spectroscopy. For a sample of 20 optically faint sources in CDFS, we compile 0.4-24 μm photometry, relying heavily on the Spitzer Space Telescope. We estimate photometric redshifts for 17 of these 20 sources. We find that these AGNs are optically faint, both because they lie at significantly higher redshifts (median z ∼ 1.6) than most X-ray-selected AGNs, and because their spectra are much redder than standard AGNs. They have 2-8 keV X-ray luminosities in the Seyfert range, unlike the QSO luminosities of optically faint AGNs found in shallow wide-field surveys. Their contribution to the X-ray Seyfert luminosity function is comparable to that of z > 1 optically bright AGNs.

KW - Galaxies: active

KW - Infrared: galaxies

KW - X-rays: galaxies

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U2 - 10.1086/430398

DO - 10.1086/430398

M3 - Review article

AN - SCOPUS:24144440419

SN - 0004-637X

VL - 627

SP - 134

EP - 139

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1 I

ER -

Why optically faint AGNs are optically faint: The spitzer perspective

Abstract

Keywords

ASJC Scopus subject areas

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