The X-Ray Properties of [CLC][ITAL]z[/ITAL][/CLC] &gt; 4 Quasars

Kaspi, S.; Brandt, W. N.; Schneider, Donald P.

doi:10.1086/301362

Cited by 41 publications

(76 citation statements)

References 45 publications

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“…consistent with the values found by Bechtold et al (1994a) and Kaspi et al (2000) within the errors.…”

Section: Q 0000−263supporting

confidence: 91%

“…From this fit they deduced a broad spectral index α ox = 1.85 whereas we find a slightly different value α ox = 1.78. Kaspi et al (2000) give a broad spectral index α ox = 1.65. The errors on the α ox have been estimated to be < ∼ 5% as in Sect.…”

Section: Radio-quiet Objectsmentioning

confidence: 99%

“…From ASCA data (as well as ROSAT data in the case of PKS 2126−158) Cappi et al (1997) claim excess absorption towards the radio-loud objects. No excess absorption towards the radio-quiet objects was found from ROSAT observations (Bechtold et al 1994a;Reimers et al 1995;Kaspi et al 2000).…”

Section: Introductionmentioning

confidence: 95%

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XMM-Newton observations of four high-z quasars

Ferrero

Brinkmann

2003

A&A

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Abstract. We present the results of XMM-Newton observations of four high-z quasars, two radio-loud and two radio-quiet. One of the radio-loud objects, PKS 2126−158, clearly shows absorption in excess of the galactic value as claimed before from ASCA and ROSAT observations. For PKS 2149−306 the evidence for excess absorption is only marginal in contrast to previous results. The location of the absorber in PKS 2126−158 is compatible with the redshift of the source. Both, a warm and a cold absorber are allowed by the X-ray data. Both quasars have very flat photon spectra (Γ < ∼ 1.5) and the high photon statistics reveal small deviations from a simple power law form. For the two radio-quiet objects, Q 0000−263 and Q 1442+2931, we determine, for the first time, reliable spectral parameters. Both quasars have steeper power laws (Γ ∼ 2) and show absorption consistent with the galactic value, similar to radio-quiet quasars at low redshifts. In the case of Q 0000−263 the presence of the damped Lyα system (N(HI) ∼ 2.6 × 10 21 cm −2 at z = 3.39) cannot be examined further due to the limited photon statistics in all instruments.

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“…consistent with the values found by Bechtold et al (1994a) and Kaspi et al (2000) within the errors.…”

Section: Q 0000−263supporting

confidence: 91%

Section: Radio-quiet Objectsmentioning

confidence: 99%

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XMM-Newton observations of four high-z quasars

Ferrero

Brinkmann

2003

A&A

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“…For a low redshift comparison sample, we use the compilation of ROSAT all-sky survey and pointed observations for radio-quiet quasars (Yuan et al 1998) and radio-loud quasars and blazars (Brinkman et al 1997), supplemented with observations of other high redshift quasars from the literature (Schneider et al 1998;Kaspi, Brandt & Schneider 2000;Brandt et al 2001;Vignali et al 2001). Since Yuan et al (1998) and Brinkman et al (1997) did not list α ox , we computed it from the listed unbsorbed X-ray flux density (0.1-2.4keV), assuming that the spectrum is a power law, with energy index Γ x with the best fit Γ x listed by Yuan et al (1998).…”

Section: The Evolution Of α Ox For Radio-quiet Quasarsmentioning

confidence: 99%

ChandraSurvey of Radio‐quiet, High‐Redshift Quasars

Bechtold

Siemiginowska

Shields

et al. 2003

ApJ

110

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We 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 α ≥ 0.02. The high redshift quasars have supermassive black holes with masses ∼ 10 10 M ⊙ , 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 τ (IGM) < 10 6 , compared to the lower limit from the spectrum of Lyα and Lyβ, which implies τ (IGM) > 20.

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“…At z [ 4 our knowledge about the X-ray properties of quasars is unfortunately quite limited (e.g., Kaspi, Brandt, & Schneider 2000 and references therein). To date it has been possible only to obtain X-ray spectra for four z [ 4 quasars.…”

Section: Introductionmentioning

confidence: 99%

An [ITAL]XMM[/ITAL]-[ITAL]Newton[/ITAL] Detection of the [CLC][ITAL]z[/ITAL][/CLC] = 5.80 X-Ray–Weak Quasar SDSS[CLC]p[/CLC] J104433.04-012502.2

Brandt

Guainazzi²,

Kaspi

et al. 2001

The Astronomical Journal

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We report on an XMM-Newton observation of the most distant known quasar, SDSSp J104433.04[ 012502.2, at z \ 5.80. We have detected this quasar with high signiÐcance in the rest-frame 3.4È13.6 keV band, making it the most distant cosmic object detected in X-rays ; 32^9 counts were collected. SDSSp J104433.04[012502.2 is notably X-rayÈweak relative to other luminous, optically selected quasars, with and a 3.4È13.6 keV luminosity of B1.8 ] 1044 ergs s~1. The most likely reason for a ox \ [1.91^0.05 its X-ray weakness is heavy absorption with cm~2, as is seen in some broad absorption line N H Z 1024 quasars and related objects ; we discuss this and other possibilities. High-quality spectroscopy from 0.95È 1.10 km to search for blueshifted C IV absorption may elucidate the origin of the X-ray weakness.

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The X-Ray Properties of [CLC][ITAL]z[/ITAL][/CLC] > 4 Quasars

Cited by 41 publications

References 45 publications

XMM-Newton observations of four high-z quasars

XMM-Newton observations of four high-z quasars

ChandraSurvey of Radio‐quiet, High‐Redshift Quasars

An [ITAL]XMM[/ITAL]-[ITAL]Newton[/ITAL] Detection of the [CLC][ITAL]z[/ITAL][/CLC] = 5.80 X-Ray–Weak Quasar SDSS[CLC]p[/CLC] J104433.04-012502.2

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