Abstract
The deep X-ray, optical, and far-infrared fields that constitute the Great Observatories Origins Deep Survey (GOODS) are sensitive to obscured active galactic nuclei (AGNs; NH≳1022 cm-2) at the quasar epoch (z ∼ 2-3), as well as to unobscured AGNs as distant as z ∼ 7. Luminous X-ray emission is a sign of accretion onto a supermassive black hole and thus reveals all but the most heavily obscured AGNs. We combine X-ray luminosity functions with appropriate spectral energy distributions for AGNs to model the X-ray, optical, and farinfrared flux distributions of the X-ray sources in the GOODS fields. A simple model based on the unified paradigm for AGNs, with ∼3 times as many obscured AGNs as unobscured, successfully reproduces the z-band flux distributions measured in the deep Hubble Space Telescope ACS observations of the GOODS-North and GOODS-South fields. This model is also consistent with the observed spectroscopic and photometric redshift distributions once selection effects are considered. The previously reported discrepancy between observed spectroscopic redshift distributions and the predictions of population synthesis models for the X-ray background can be explained by a bias against the most heavily obscured AGNs generated by both X-ray observations and the identification of sources via optical spectroscopy. We predict the AGN number counts for Spitzer MIPS 24 μm and IRAC 3.6-8 μm observations in the GOODS fields, which will verify whether most AGNs in the early universe are obscured in the optical. Such AGNs should be very bright far-infrared sources and include some obscured AGNs missed even by X-ray observations.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 123-135 |
| Number of pages | 13 |
| Journal | Astrophysical Journal |
| Volume | 616 |
| Issue number | 1 I |
| DOIs | |
| State | Published - Nov 20 2004 |
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All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
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Obscured active galactic nuclei and the X-RAY, optical, and far-infrared number counts of active galactic nuclei in the goods fields. / Treister, Ezequiel; Megan Urry, C.; Chatzichristou, Eleni; Bauer, Franz; Alexander, David M.; Koekemoer, Anton; Van Duyne, Jeffrey; Brandt, William N.; Bergeron, Jacqueline; Stern, Daniel; Moustakas, Leonidas A.; Chary, Ranga Ram; Conselice, Christopher; Cristiani, Stefano; Grogin, Norman.
In: Astrophysical Journal, Vol. 616, No. 1 I, 20.11.2004, p. 123-135.Research output: Contribution to journal › Article
TY - JOUR
T1 - Obscured active galactic nuclei and the X-RAY, optical, and far-infrared number counts of active galactic nuclei in the goods fields
AU - Treister, Ezequiel
AU - Megan Urry, C.
AU - Chatzichristou, Eleni
AU - Bauer, Franz
AU - Alexander, David M.
AU - Koekemoer, Anton
AU - Van Duyne, Jeffrey
AU - Brandt, William N.
AU - Bergeron, Jacqueline
AU - Stern, Daniel
AU - Moustakas, Leonidas A.
AU - Chary, Ranga Ram
AU - Conselice, Christopher
AU - Cristiani, Stefano
AU - Grogin, Norman
PY - 2004/11/20
Y1 - 2004/11/20
N2 - The deep X-ray, optical, and far-infrared fields that constitute the Great Observatories Origins Deep Survey (GOODS) are sensitive to obscured active galactic nuclei (AGNs; NH≳1022 cm-2) at the quasar epoch (z ∼ 2-3), as well as to unobscured AGNs as distant as z ∼ 7. Luminous X-ray emission is a sign of accretion onto a supermassive black hole and thus reveals all but the most heavily obscured AGNs. We combine X-ray luminosity functions with appropriate spectral energy distributions for AGNs to model the X-ray, optical, and farinfrared flux distributions of the X-ray sources in the GOODS fields. A simple model based on the unified paradigm for AGNs, with ∼3 times as many obscured AGNs as unobscured, successfully reproduces the z-band flux distributions measured in the deep Hubble Space Telescope ACS observations of the GOODS-North and GOODS-South fields. This model is also consistent with the observed spectroscopic and photometric redshift distributions once selection effects are considered. The previously reported discrepancy between observed spectroscopic redshift distributions and the predictions of population synthesis models for the X-ray background can be explained by a bias against the most heavily obscured AGNs generated by both X-ray observations and the identification of sources via optical spectroscopy. We predict the AGN number counts for Spitzer MIPS 24 μm and IRAC 3.6-8 μm observations in the GOODS fields, which will verify whether most AGNs in the early universe are obscured in the optical. Such AGNs should be very bright far-infrared sources and include some obscured AGNs missed even by X-ray observations.
AB - The deep X-ray, optical, and far-infrared fields that constitute the Great Observatories Origins Deep Survey (GOODS) are sensitive to obscured active galactic nuclei (AGNs; NH≳1022 cm-2) at the quasar epoch (z ∼ 2-3), as well as to unobscured AGNs as distant as z ∼ 7. Luminous X-ray emission is a sign of accretion onto a supermassive black hole and thus reveals all but the most heavily obscured AGNs. We combine X-ray luminosity functions with appropriate spectral energy distributions for AGNs to model the X-ray, optical, and farinfrared flux distributions of the X-ray sources in the GOODS fields. A simple model based on the unified paradigm for AGNs, with ∼3 times as many obscured AGNs as unobscured, successfully reproduces the z-band flux distributions measured in the deep Hubble Space Telescope ACS observations of the GOODS-North and GOODS-South fields. This model is also consistent with the observed spectroscopic and photometric redshift distributions once selection effects are considered. The previously reported discrepancy between observed spectroscopic redshift distributions and the predictions of population synthesis models for the X-ray background can be explained by a bias against the most heavily obscured AGNs generated by both X-ray observations and the identification of sources via optical spectroscopy. We predict the AGN number counts for Spitzer MIPS 24 μm and IRAC 3.6-8 μm observations in the GOODS fields, which will verify whether most AGNs in the early universe are obscured in the optical. Such AGNs should be very bright far-infrared sources and include some obscured AGNs missed even by X-ray observations.
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U2 - 10.1086/424891
DO - 10.1086/424891
M3 - Article
AN - SCOPUS:19944430815
VL - 616
SP - 123
EP - 135
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1 I
ER -