Chandra Survey of Radio-quiet, High-redshift Quasars

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dc.creatorBechtold, Jill
dc.creatorSiemiginowska, Aneta
dc.creatorShields, Joseph
dc.creatorCzerny, Bozena
dc.creatorJaniuk, Agnieszka
dc.creatorHamann, Fred
dc.creatorAldcroft, Thomas L.
dc.creatorElvis, Martin
dc.creatorDobrzycki, Adam
dc.date2002-04-26
dc.date.accessioned2026-07-07T10:31:14Z
dc.date.available2026-07-07T10:31:14Z
dc.descriptionWe observed 17 optically-selected, radio-quiet high-redshift quasars with the Chandra Observatory ACIS, and detected 16 of them. The quasars have redshift between 3.70 and 6.28 and include the highest redshift quasars known. When compared to 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 where the accretion flow is described by a cold, optically-thick accretion disk surrounded by a hot, optically thin corona, provided the viscosity parameter alpha >= 0.02. The high redshift quasars have supermassive black holes with masses ~10^{10} M_{sun}, and are accreting material at ~0.1 the Eddington limit. We detect 10 X-ray photons from the z=6.28 quasar SDS 1030+0524, which may 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 tau(IGM) < 10^6, compared to the lower limit from the spectrum of Lyalpha and Lybeta, which implies tau(IGM) > 20.
dc.descriptionAccepted for publication in the Astrophysical Journal
dc.identifierhttps://arxiv.org/abs/astro-ph/0204462
dc.identifierhttp://arxiv.org/abs/astro-ph/0204462
dc.identifierAstrophys.J.588:119-127,2003
dc.identifierdoi:10.1086/378724
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/178343
dc.subjectAstrophysics
dc.titleChandra Survey of Radio-quiet, High-redshift Quasars
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