NuSTAR and XMM-Newton observations of luminous, heavily obscured, wise-selected quasars at Z2

D. Stern, G. B. Lansbury, R. J. Assef, W. N. Brandt, D. M. Alexander, D. R. Ballantyne, M. Baloković, F. E. Bauer, D. Benford, A. Blain, S. E. Boggs, C. Bridge, M. Brightman, F. E. Christensen, A. Comastri, W. W. Craig, A. Del Moro, P. R.M. Eisenhardt, P. Gandhi, R. L. GriffithC. J. Hailey, F. A. Harrison, R. C. Hickox, T. H. Jarrett, M. Koss, S. Lake, S. M. Lamassa, B. Luo, C. W. Tsai, C. M. Urry, D. J. Walton, E. L. Wright, J. Wu, L. Yan, W. W. Zhang

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Abstract

We report on a NuSTAR and XMM-Newton program that has observed a sample of three extremely luminous, heavily obscured WISE-selected active galactic nuclei (AGNs) at z 2 across a broad X-ray band (0.1-79 keV). The parent sample, selected to be faint or undetected in the WISE 3.4 μm (W1) and 4.6 μm (W2) bands but bright at 12 μm (W3) and 22 μm (W4), are extremely rare, with only 1000 so-called "W1W2-dropouts" across the extragalactic sky. Optical spectroscopy reveals typical redshifts of z 2 for this population, implying rest-frame mid-IR luminosities of νL ν(6 μm) 6 × 1046 erg s-1 and bolometric luminosities that can exceed L bol 1014 L . The corresponding intrinsic, unobscured hard X-ray luminosities are L(2-10 keV) 4 × 1045 erg s-1 for typical quasar templates. These are among the most AGNs known, though the optical spectra rarely show evidence of a broad-line region and the selection criteria imply heavy obscuration even at rest-frame 1.5 μm. We designed our X-ray observations to obtain robust detections for gas column densities N H ≤ 1024 cm-2. In fact, the sources prove to be fainter than these predictions. Two of the sources were observed by both NuSTAR and XMM-Newton, with neither being detected by NuSTAR (f 3-24 keV ≲ 10-13 erg cm-2 s-1), and one being faintly detected by XMM-Newton (f 0.5-10 keV 5 × 10-15 erg cm-2 s-1). A third source was observed only with XMM-Newton, yielding a faint detection (f 0.5-10 keV 7 × 10-15 erg cm-2 s-1). The X-ray data imply these sources are either X-ray weak, or are heavily obscured by column densities N H ≳ 1024 cm-2. The combined X-ray and mid-IR analysis seems to favor this second possibility, implying the sources are extremely obscured, consistent with Compton-thick, luminous quasars. The discovery of a significant population of heavily obscured, extremely luminous AGNs would not conform to the standard paradigm of a receding torus, in which more luminous quasars are less likely to be obscured, and instead suggests that an additional source of obscuration is present in these extreme sources.

Original languageEnglish (US)
Article number102
JournalAstrophysical Journal
Volume794
Issue number2
DOIs
StatePublished - Oct 20 2014

Fingerprint

XMM-Newton telescope
quasars
newton
erg
active galactic nuclei
Wide-field Infrared Survey Explorer
x rays
luminosity
occultation
dropouts
sky
optical spectrum
spectroscopy
templates
prediction
gas
predictions
gases

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Stern, D., Lansbury, G. B., Assef, R. J., Brandt, W. N., Alexander, D. M., Ballantyne, D. R., ... Zhang, W. W. (2014). NuSTAR and XMM-Newton observations of luminous, heavily obscured, wise-selected quasars at Z2. Astrophysical Journal, 794(2), [102]. https://doi.org/10.1088/0004-637X/794/2/102
Stern, D. ; Lansbury, G. B. ; Assef, R. J. ; Brandt, W. N. ; Alexander, D. M. ; Ballantyne, D. R. ; Baloković, M. ; Bauer, F. E. ; Benford, D. ; Blain, A. ; Boggs, S. E. ; Bridge, C. ; Brightman, M. ; Christensen, F. E. ; Comastri, A. ; Craig, W. W. ; Del Moro, A. ; Eisenhardt, P. R.M. ; Gandhi, P. ; Griffith, R. L. ; Hailey, C. J. ; Harrison, F. A. ; Hickox, R. C. ; Jarrett, T. H. ; Koss, M. ; Lake, S. ; Lamassa, S. M. ; Luo, B. ; Tsai, C. W. ; Urry, C. M. ; Walton, D. J. ; Wright, E. L. ; Wu, J. ; Yan, L. ; Zhang, W. W. / NuSTAR and XMM-Newton observations of luminous, heavily obscured, wise-selected quasars at Z2. In: Astrophysical Journal. 2014 ; Vol. 794, No. 2.
@article{5828c18e070547a5afb74b1a824af4c6,
title = "NuSTAR and XMM-Newton observations of luminous, heavily obscured, wise-selected quasars at Z2",
abstract = "We report on a NuSTAR and XMM-Newton program that has observed a sample of three extremely luminous, heavily obscured WISE-selected active galactic nuclei (AGNs) at z 2 across a broad X-ray band (0.1-79 keV). The parent sample, selected to be faint or undetected in the WISE 3.4 μm (W1) and 4.6 μm (W2) bands but bright at 12 μm (W3) and 22 μm (W4), are extremely rare, with only 1000 so-called {"}W1W2-dropouts{"} across the extragalactic sky. Optical spectroscopy reveals typical redshifts of z 2 for this population, implying rest-frame mid-IR luminosities of νL ν(6 μm) 6 × 1046 erg s-1 and bolometric luminosities that can exceed L bol 1014 L . The corresponding intrinsic, unobscured hard X-ray luminosities are L(2-10 keV) 4 × 1045 erg s-1 for typical quasar templates. These are among the most AGNs known, though the optical spectra rarely show evidence of a broad-line region and the selection criteria imply heavy obscuration even at rest-frame 1.5 μm. We designed our X-ray observations to obtain robust detections for gas column densities N H ≤ 1024 cm-2. In fact, the sources prove to be fainter than these predictions. Two of the sources were observed by both NuSTAR and XMM-Newton, with neither being detected by NuSTAR (f 3-24 keV ≲ 10-13 erg cm-2 s-1), and one being faintly detected by XMM-Newton (f 0.5-10 keV 5 × 10-15 erg cm-2 s-1). A third source was observed only with XMM-Newton, yielding a faint detection (f 0.5-10 keV 7 × 10-15 erg cm-2 s-1). The X-ray data imply these sources are either X-ray weak, or are heavily obscured by column densities N H ≳ 1024 cm-2. The combined X-ray and mid-IR analysis seems to favor this second possibility, implying the sources are extremely obscured, consistent with Compton-thick, luminous quasars. The discovery of a significant population of heavily obscured, extremely luminous AGNs would not conform to the standard paradigm of a receding torus, in which more luminous quasars are less likely to be obscured, and instead suggests that an additional source of obscuration is present in these extreme sources.",
author = "D. Stern and Lansbury, {G. B.} and Assef, {R. J.} and Brandt, {W. N.} and Alexander, {D. M.} and Ballantyne, {D. R.} and M. Baloković and Bauer, {F. E.} and D. Benford and A. Blain and Boggs, {S. E.} and C. Bridge and M. Brightman and Christensen, {F. E.} and A. Comastri and Craig, {W. W.} and {Del Moro}, A. and Eisenhardt, {P. R.M.} and P. Gandhi and Griffith, {R. L.} and Hailey, {C. J.} and Harrison, {F. A.} and Hickox, {R. C.} and Jarrett, {T. H.} and M. Koss and S. Lake and Lamassa, {S. M.} and B. Luo and Tsai, {C. W.} and Urry, {C. M.} and Walton, {D. J.} and Wright, {E. L.} and J. Wu and L. Yan and Zhang, {W. W.}",
year = "2014",
month = "10",
day = "20",
doi = "10.1088/0004-637X/794/2/102",
language = "English (US)",
volume = "794",
journal = "Astrophysical Journal",
issn = "0004-637X",
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Stern, D, Lansbury, GB, Assef, RJ, Brandt, WN, Alexander, DM, Ballantyne, DR, Baloković, M, Bauer, FE, Benford, D, Blain, A, Boggs, SE, Bridge, C, Brightman, M, Christensen, FE, Comastri, A, Craig, WW, Del Moro, A, Eisenhardt, PRM, Gandhi, P, Griffith, RL, Hailey, CJ, Harrison, FA, Hickox, RC, Jarrett, TH, Koss, M, Lake, S, Lamassa, SM, Luo, B, Tsai, CW, Urry, CM, Walton, DJ, Wright, EL, Wu, J, Yan, L & Zhang, WW 2014, 'NuSTAR and XMM-Newton observations of luminous, heavily obscured, wise-selected quasars at Z2', Astrophysical Journal, vol. 794, no. 2, 102. https://doi.org/10.1088/0004-637X/794/2/102

NuSTAR and XMM-Newton observations of luminous, heavily obscured, wise-selected quasars at Z2. / Stern, D.; Lansbury, G. B.; Assef, R. J.; Brandt, W. N.; Alexander, D. M.; Ballantyne, D. R.; Baloković, M.; Bauer, F. E.; Benford, D.; Blain, A.; Boggs, S. E.; Bridge, C.; Brightman, M.; Christensen, F. E.; Comastri, A.; Craig, W. W.; Del Moro, A.; Eisenhardt, P. R.M.; Gandhi, P.; Griffith, R. L.; Hailey, C. J.; Harrison, F. A.; Hickox, R. C.; Jarrett, T. H.; Koss, M.; Lake, S.; Lamassa, S. M.; Luo, B.; Tsai, C. W.; Urry, C. M.; Walton, D. J.; Wright, E. L.; Wu, J.; Yan, L.; Zhang, W. W.

In: Astrophysical Journal, Vol. 794, No. 2, 102, 20.10.2014.

Research output: Contribution to journalArticle

TY - JOUR

T1 - NuSTAR and XMM-Newton observations of luminous, heavily obscured, wise-selected quasars at Z2

AU - Stern, D.

AU - Lansbury, G. B.

AU - Assef, R. J.

AU - Brandt, W. N.

AU - Alexander, D. M.

AU - Ballantyne, D. R.

AU - Baloković, M.

AU - Bauer, F. E.

AU - Benford, D.

AU - Blain, A.

AU - Boggs, S. E.

AU - Bridge, C.

AU - Brightman, M.

AU - Christensen, F. E.

AU - Comastri, A.

AU - Craig, W. W.

AU - Del Moro, A.

AU - Eisenhardt, P. R.M.

AU - Gandhi, P.

AU - Griffith, R. L.

AU - Hailey, C. J.

AU - Harrison, F. A.

AU - Hickox, R. C.

AU - Jarrett, T. H.

AU - Koss, M.

AU - Lake, S.

AU - Lamassa, S. M.

AU - Luo, B.

AU - Tsai, C. W.

AU - Urry, C. M.

AU - Walton, D. J.

AU - Wright, E. L.

AU - Wu, J.

AU - Yan, L.

AU - Zhang, W. W.

PY - 2014/10/20

Y1 - 2014/10/20

N2 - We report on a NuSTAR and XMM-Newton program that has observed a sample of three extremely luminous, heavily obscured WISE-selected active galactic nuclei (AGNs) at z 2 across a broad X-ray band (0.1-79 keV). The parent sample, selected to be faint or undetected in the WISE 3.4 μm (W1) and 4.6 μm (W2) bands but bright at 12 μm (W3) and 22 μm (W4), are extremely rare, with only 1000 so-called "W1W2-dropouts" across the extragalactic sky. Optical spectroscopy reveals typical redshifts of z 2 for this population, implying rest-frame mid-IR luminosities of νL ν(6 μm) 6 × 1046 erg s-1 and bolometric luminosities that can exceed L bol 1014 L . The corresponding intrinsic, unobscured hard X-ray luminosities are L(2-10 keV) 4 × 1045 erg s-1 for typical quasar templates. These are among the most AGNs known, though the optical spectra rarely show evidence of a broad-line region and the selection criteria imply heavy obscuration even at rest-frame 1.5 μm. We designed our X-ray observations to obtain robust detections for gas column densities N H ≤ 1024 cm-2. In fact, the sources prove to be fainter than these predictions. Two of the sources were observed by both NuSTAR and XMM-Newton, with neither being detected by NuSTAR (f 3-24 keV ≲ 10-13 erg cm-2 s-1), and one being faintly detected by XMM-Newton (f 0.5-10 keV 5 × 10-15 erg cm-2 s-1). A third source was observed only with XMM-Newton, yielding a faint detection (f 0.5-10 keV 7 × 10-15 erg cm-2 s-1). The X-ray data imply these sources are either X-ray weak, or are heavily obscured by column densities N H ≳ 1024 cm-2. The combined X-ray and mid-IR analysis seems to favor this second possibility, implying the sources are extremely obscured, consistent with Compton-thick, luminous quasars. The discovery of a significant population of heavily obscured, extremely luminous AGNs would not conform to the standard paradigm of a receding torus, in which more luminous quasars are less likely to be obscured, and instead suggests that an additional source of obscuration is present in these extreme sources.

AB - We report on a NuSTAR and XMM-Newton program that has observed a sample of three extremely luminous, heavily obscured WISE-selected active galactic nuclei (AGNs) at z 2 across a broad X-ray band (0.1-79 keV). The parent sample, selected to be faint or undetected in the WISE 3.4 μm (W1) and 4.6 μm (W2) bands but bright at 12 μm (W3) and 22 μm (W4), are extremely rare, with only 1000 so-called "W1W2-dropouts" across the extragalactic sky. Optical spectroscopy reveals typical redshifts of z 2 for this population, implying rest-frame mid-IR luminosities of νL ν(6 μm) 6 × 1046 erg s-1 and bolometric luminosities that can exceed L bol 1014 L . The corresponding intrinsic, unobscured hard X-ray luminosities are L(2-10 keV) 4 × 1045 erg s-1 for typical quasar templates. These are among the most AGNs known, though the optical spectra rarely show evidence of a broad-line region and the selection criteria imply heavy obscuration even at rest-frame 1.5 μm. We designed our X-ray observations to obtain robust detections for gas column densities N H ≤ 1024 cm-2. In fact, the sources prove to be fainter than these predictions. Two of the sources were observed by both NuSTAR and XMM-Newton, with neither being detected by NuSTAR (f 3-24 keV ≲ 10-13 erg cm-2 s-1), and one being faintly detected by XMM-Newton (f 0.5-10 keV 5 × 10-15 erg cm-2 s-1). A third source was observed only with XMM-Newton, yielding a faint detection (f 0.5-10 keV 7 × 10-15 erg cm-2 s-1). The X-ray data imply these sources are either X-ray weak, or are heavily obscured by column densities N H ≳ 1024 cm-2. The combined X-ray and mid-IR analysis seems to favor this second possibility, implying the sources are extremely obscured, consistent with Compton-thick, luminous quasars. The discovery of a significant population of heavily obscured, extremely luminous AGNs would not conform to the standard paradigm of a receding torus, in which more luminous quasars are less likely to be obscured, and instead suggests that an additional source of obscuration is present in these extreme sources.

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