Infrared to x-ray spectral energy distributions of high redshift quasars

Jill Bechtold, Martin Elvis, Fabrizio Fiore, Olga Kuhn, Roc M. Cutri, Jonathan C. Mcdowell, Marcia J Rieke, Aneta Siemiginowska, Belinda J. Wilkes

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

We have observed 14 quasars with z>2.8 with the ROSAT-PSPC, and detected 12 of them, including the z=4.11 quasar 0000-263. We present the first x-ray spectrum of a radio quiet quasar with z>3, 1946+768. Its x-ray spectrum is consistent with a power law with spectral index αE = 1.8+2.1-1.4 and no evidence for absorption in excess of the galactic column [αE=1.00+0.28-0.32 assuming NH=NH(Gal)]. A PSPC hardness ratio is used to constrain the x-ray spectral properties of the quasars for which there were less than 100 photons detected. For the radio quiet quasars, 〈αE〉≈1.2, if one assumes that there is no absorption in excess of the galactic column. We combine the x-ray data with new ground based optical and near-IR spectrophotometry obtained at the Steward 2.3 m and Multiple Mirror Telescope, and data from the literature. The spectral energy distributions are compared to those of low redshift objects. For the radio quiet quasars with z>2.5, the mean 〈αox〉∼1.8. This is larger than the mean for quasars with z<2.5, but consistent with the expected value for quasars with the high optical luminosities of the objects in this sample. For the radio-loud quasars, 〈αox〉∼1.4, independent of redshift. This is smaller than the expected value for the optically luminous, high redshift objects in this sample, if they are mostly GHz peaked radio sources and hence comparable to steep-spectrum, compact radio sources at lower redshift. Finally, we compare the spectral energy distributions of two representative objects to the predicted spectrum of a thin accretion disk in the Kerr geometry, and discuss the uncertainties in deriving black hole masses and mass accretion rates.

Original languageEnglish (US)
Pages (from-to)374-394
Number of pages21
JournalAstronomical Journal
Volume108
Issue number2
StatePublished - Aug 1994

Fingerprint

spectral energy distribution
quasars
radio
energy
x rays
x ray spectra
accretion
spectrophotometry
hardness
distribution
power law
geometry
accretion disks
luminosity
telescopes
mirrors
photons

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Bechtold, J., Elvis, M., Fiore, F., Kuhn, O., Cutri, R. M., Mcdowell, J. C., ... Wilkes, B. J. (1994). Infrared to x-ray spectral energy distributions of high redshift quasars. Astronomical Journal, 108(2), 374-394.

Infrared to x-ray spectral energy distributions of high redshift quasars. / Bechtold, Jill; Elvis, Martin; Fiore, Fabrizio; Kuhn, Olga; Cutri, Roc M.; Mcdowell, Jonathan C.; Rieke, Marcia J; Siemiginowska, Aneta; Wilkes, Belinda J.

In: Astronomical Journal, Vol. 108, No. 2, 08.1994, p. 374-394.

Research output: Contribution to journalArticle

Bechtold, J, Elvis, M, Fiore, F, Kuhn, O, Cutri, RM, Mcdowell, JC, Rieke, MJ, Siemiginowska, A & Wilkes, BJ 1994, 'Infrared to x-ray spectral energy distributions of high redshift quasars', Astronomical Journal, vol. 108, no. 2, pp. 374-394.
Bechtold J, Elvis M, Fiore F, Kuhn O, Cutri RM, Mcdowell JC et al. Infrared to x-ray spectral energy distributions of high redshift quasars. Astronomical Journal. 1994 Aug;108(2):374-394.
Bechtold, Jill ; Elvis, Martin ; Fiore, Fabrizio ; Kuhn, Olga ; Cutri, Roc M. ; Mcdowell, Jonathan C. ; Rieke, Marcia J ; Siemiginowska, Aneta ; Wilkes, Belinda J. / Infrared to x-ray spectral energy distributions of high redshift quasars. In: Astronomical Journal. 1994 ; Vol. 108, No. 2. pp. 374-394.
@article{15f1d0afad9f4ea09f67b15174062077,
title = "Infrared to x-ray spectral energy distributions of high redshift quasars",
abstract = "We have observed 14 quasars with z>2.8 with the ROSAT-PSPC, and detected 12 of them, including the z=4.11 quasar 0000-263. We present the first x-ray spectrum of a radio quiet quasar with z>3, 1946+768. Its x-ray spectrum is consistent with a power law with spectral index αE = 1.8+2.1-1.4 and no evidence for absorption in excess of the galactic column [αE=1.00+0.28-0.32 assuming NH=NH(Gal)]. A PSPC hardness ratio is used to constrain the x-ray spectral properties of the quasars for which there were less than 100 photons detected. For the radio quiet quasars, 〈αE〉≈1.2, if one assumes that there is no absorption in excess of the galactic column. We combine the x-ray data with new ground based optical and near-IR spectrophotometry obtained at the Steward 2.3 m and Multiple Mirror Telescope, and data from the literature. The spectral energy distributions are compared to those of low redshift objects. For the radio quiet quasars with z>2.5, the mean 〈αox〉∼1.8. This is larger than the mean for quasars with z<2.5, but consistent with the expected value for quasars with the high optical luminosities of the objects in this sample. For the radio-loud quasars, 〈αox〉∼1.4, independent of redshift. This is smaller than the expected value for the optically luminous, high redshift objects in this sample, if they are mostly GHz peaked radio sources and hence comparable to steep-spectrum, compact radio sources at lower redshift. Finally, we compare the spectral energy distributions of two representative objects to the predicted spectrum of a thin accretion disk in the Kerr geometry, and discuss the uncertainties in deriving black hole masses and mass accretion rates.",
author = "Jill Bechtold and Martin Elvis and Fabrizio Fiore and Olga Kuhn and Cutri, {Roc M.} and Mcdowell, {Jonathan C.} and Rieke, {Marcia J} and Aneta Siemiginowska and Wilkes, {Belinda J.}",
year = "1994",
month = "8",
language = "English (US)",
volume = "108",
pages = "374--394",
journal = "Astronomical Journal",
issn = "0004-6256",
publisher = "IOP Publishing Ltd.",
number = "2",

}

TY - JOUR

T1 - Infrared to x-ray spectral energy distributions of high redshift quasars

AU - Bechtold, Jill

AU - Elvis, Martin

AU - Fiore, Fabrizio

AU - Kuhn, Olga

AU - Cutri, Roc M.

AU - Mcdowell, Jonathan C.

AU - Rieke, Marcia J

AU - Siemiginowska, Aneta

AU - Wilkes, Belinda J.

PY - 1994/8

Y1 - 1994/8

N2 - We have observed 14 quasars with z>2.8 with the ROSAT-PSPC, and detected 12 of them, including the z=4.11 quasar 0000-263. We present the first x-ray spectrum of a radio quiet quasar with z>3, 1946+768. Its x-ray spectrum is consistent with a power law with spectral index αE = 1.8+2.1-1.4 and no evidence for absorption in excess of the galactic column [αE=1.00+0.28-0.32 assuming NH=NH(Gal)]. A PSPC hardness ratio is used to constrain the x-ray spectral properties of the quasars for which there were less than 100 photons detected. For the radio quiet quasars, 〈αE〉≈1.2, if one assumes that there is no absorption in excess of the galactic column. We combine the x-ray data with new ground based optical and near-IR spectrophotometry obtained at the Steward 2.3 m and Multiple Mirror Telescope, and data from the literature. The spectral energy distributions are compared to those of low redshift objects. For the radio quiet quasars with z>2.5, the mean 〈αox〉∼1.8. This is larger than the mean for quasars with z<2.5, but consistent with the expected value for quasars with the high optical luminosities of the objects in this sample. For the radio-loud quasars, 〈αox〉∼1.4, independent of redshift. This is smaller than the expected value for the optically luminous, high redshift objects in this sample, if they are mostly GHz peaked radio sources and hence comparable to steep-spectrum, compact radio sources at lower redshift. Finally, we compare the spectral energy distributions of two representative objects to the predicted spectrum of a thin accretion disk in the Kerr geometry, and discuss the uncertainties in deriving black hole masses and mass accretion rates.

AB - We have observed 14 quasars with z>2.8 with the ROSAT-PSPC, and detected 12 of them, including the z=4.11 quasar 0000-263. We present the first x-ray spectrum of a radio quiet quasar with z>3, 1946+768. Its x-ray spectrum is consistent with a power law with spectral index αE = 1.8+2.1-1.4 and no evidence for absorption in excess of the galactic column [αE=1.00+0.28-0.32 assuming NH=NH(Gal)]. A PSPC hardness ratio is used to constrain the x-ray spectral properties of the quasars for which there were less than 100 photons detected. For the radio quiet quasars, 〈αE〉≈1.2, if one assumes that there is no absorption in excess of the galactic column. We combine the x-ray data with new ground based optical and near-IR spectrophotometry obtained at the Steward 2.3 m and Multiple Mirror Telescope, and data from the literature. The spectral energy distributions are compared to those of low redshift objects. For the radio quiet quasars with z>2.5, the mean 〈αox〉∼1.8. This is larger than the mean for quasars with z<2.5, but consistent with the expected value for quasars with the high optical luminosities of the objects in this sample. For the radio-loud quasars, 〈αox〉∼1.4, independent of redshift. This is smaller than the expected value for the optically luminous, high redshift objects in this sample, if they are mostly GHz peaked radio sources and hence comparable to steep-spectrum, compact radio sources at lower redshift. Finally, we compare the spectral energy distributions of two representative objects to the predicted spectrum of a thin accretion disk in the Kerr geometry, and discuss the uncertainties in deriving black hole masses and mass accretion rates.

UR - http://www.scopus.com/inward/record.url?scp=0009156317&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0009156317&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0009156317

VL - 108

SP - 374

EP - 394

JO - Astronomical Journal

JF - Astronomical Journal

SN - 0004-6256

IS - 2

ER -