Obscured active galactic nuclei and the X-RAY, optical, and far-infrared number counts of active galactic nuclei in the goods fields

Ezequiel Treister, C. Megan Urry, Eleni Chatzichristou, Franz Bauer, David M. Alexander, Anton Koekemoer, Jeffrey Van Duyne, William N. Brandt, Jacqueline Bergeron, Daniel Stern, Leonidas A. Moustakas, Ranga Ram Chary, Christopher Conselice, Stefano Cristiani, Norman Grogin

Research output: Contribution to journalArticle

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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 languageEnglish (US)
Pages (from-to)123-135
Number of pages13
JournalAstrophysical Journal
Volume616
Issue number1 I
DOIs
StatePublished - Nov 20 2004

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active galactic nuclei
observatories
observatory
x rays
field survey
goods
spectral energy distribution
Hubble Space Telescope
quasars
universe
spectroscopy
accretion
luminosity
time measurement
distribution
synthesis
prediction
predictions
energy

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Treister, E., Megan Urry, C., Chatzichristou, E., Bauer, F., Alexander, D. M., Koekemoer, A., ... Grogin, N. (2004). Obscured active galactic nuclei and the X-RAY, optical, and far-infrared number counts of active galactic nuclei in the goods fields. Astrophysical Journal, 616(1 I), 123-135. https://doi.org/10.1086/424891
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. / Obscured active galactic nuclei and the X-RAY, optical, and far-infrared number counts of active galactic nuclei in the goods fields. In: Astrophysical Journal. 2004 ; Vol. 616, No. 1 I. pp. 123-135.
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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.",
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Treister, E, Megan Urry, C, Chatzichristou, E, Bauer, F, Alexander, DM, Koekemoer, A, Van Duyne, J, Brandt, WN, Bergeron, J, Stern, D, Moustakas, LA, Chary, RR, Conselice, C, Cristiani, S & Grogin, N 2004, 'Obscured active galactic nuclei and the X-RAY, optical, and far-infrared number counts of active galactic nuclei in the goods fields', Astrophysical Journal, vol. 616, no. 1 I, pp. 123-135. https://doi.org/10.1086/424891

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 journalArticle

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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.

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