Chandra survey of radio-quiet, high-redshift quasars

Jill Bechtold, Aneta Siemiginowska, Joseph Shields, Bozena Czerny, Agnieszka Janiuk, Fred Hamann, Thomas L. Aldcroft, Martin Elvis, Adam Dobrzycki

Research output: Contribution to journalArticle

68 Citations (Scopus)

Abstract

We observed 17 optically selected, radio-quiet, high-redshift quasars with the Chandra ACIS and detected 16 of them. The quasars have redshifts between 3.70 and 6.28 and include the highest-redshift quasars known. When compared with low-redshift quasars observed with ROSAT, these high-redshift quasars are significantly more X-ray-quiet. We also find that the X-ray spectral index of the high-redshift objects is flatter than the average at lower redshift. These trends confirm the predictions of models in which the accretion flow is described by a cold, optically thick accretion disk surrounded by a hot, optically thin corona, provided the viscosity parameter α ≥ 0.02. The high-redshift quasars have supermassive black holes, with masses of ∼10 10 M, and are accreting material at ∼0.1 times the Eddington limit. We detect 10 X-ray photons from the z = 6.28 quasar SDSS 1030+0524, which might have a Gunn-Peterson trough and be near the redshift of reionization of the intergalactic medium. The X-ray data place an upper limit on the optical depth of the intergalactic medium, τ(IGM) < 10 6, compared to the lower limit from the spectrum of Lyα and Lyβ, which implies τ(IGM) > 20.

Original languageEnglish (US)
Pages (from-to)119-127
Number of pages9
JournalAstrophysical Journal
Volume588
Issue number1 I
DOIs
StatePublished - May 1 2003

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quasars
radio
accretion
intergalactic media
optical depth
x rays
corona
trough
viscosity
troughs
accretion disks
optical thickness
coronas
prediction
trends
photons
predictions

Keywords

  • Accretion, accretion disks
  • Intergalactic medium
  • Quasars: general
  • X-rays: galaxies

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Bechtold, J., Siemiginowska, A., Shields, J., Czerny, B., Janiuk, A., Hamann, F., ... Dobrzycki, A. (2003). Chandra survey of radio-quiet, high-redshift quasars. Astrophysical Journal, 588(1 I), 119-127. https://doi.org/10.1086/378724

Chandra survey of radio-quiet, high-redshift quasars. / Bechtold, Jill; Siemiginowska, Aneta; Shields, Joseph; Czerny, Bozena; Janiuk, Agnieszka; Hamann, Fred; Aldcroft, Thomas L.; Elvis, Martin; Dobrzycki, Adam.

In: Astrophysical Journal, Vol. 588, No. 1 I, 01.05.2003, p. 119-127.

Research output: Contribution to journalArticle

Bechtold, J, Siemiginowska, A, Shields, J, Czerny, B, Janiuk, A, Hamann, F, Aldcroft, TL, Elvis, M & Dobrzycki, A 2003, 'Chandra survey of radio-quiet, high-redshift quasars', Astrophysical Journal, vol. 588, no. 1 I, pp. 119-127. https://doi.org/10.1086/378724
Bechtold J, Siemiginowska A, Shields J, Czerny B, Janiuk A, Hamann F et al. Chandra survey of radio-quiet, high-redshift quasars. Astrophysical Journal. 2003 May 1;588(1 I):119-127. https://doi.org/10.1086/378724
Bechtold, Jill ; Siemiginowska, Aneta ; Shields, Joseph ; Czerny, Bozena ; Janiuk, Agnieszka ; Hamann, Fred ; Aldcroft, Thomas L. ; Elvis, Martin ; Dobrzycki, Adam. / Chandra survey of radio-quiet, high-redshift quasars. In: Astrophysical Journal. 2003 ; Vol. 588, No. 1 I. pp. 119-127.
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