Chandra Observations of Six QSOs at z $\approx$ 3

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dc.creatorMiyaji, Takamitsu
dc.creatorHasinger, Guenther
dc.creatorLehmann, Ingo
dc.creatorSchneider, Donald P.
dc.date2005-10-09
dc.date2006-01-16
dc.date.accessioned2026-07-07T11:24:50Z
dc.date.available2026-07-07T11:24:50Z
dc.descriptionWe report the results of our Chandra observations of six QSOs at $z\sim 3$ from the Palomer Transit Grism Survey. Our primary goal is to investigate the possible systematic change of $α_{ox}$ between $z>4$ and $z\sim 3$, between which a rapid rise of luminous QSO number density with cosmic time is observed. The summed spectrum showed a power-law spectrum with photon index of $Γ\approx 1.9$, which is similar to other unabsorbed AGNs. Combining our $z\sim 3$ QSOs with X-ray observations of QSOs at $z>4$ from literaure/archive, we find a correlation of $α_{\rm ox}$ with optical luminosity. This is consistent with the fact that the luminosity function slope of the luminous end of the X-ray selected QSOs is steeper than that of optically-selected QSOs. We discuss an upper limit to the redshift dependence of $α_{ox}$ using a Monte-Carlo simulation. Within the current statistical errors including the derived limits on the redshift dependence of $α_{\rm ox}$, we found that the behaviors of the X-ray and optically-selected QSO number densities are consistent with each other.
dc.description13 Pages, 3 Figures, Astronomical Journal in press, An entry in Table 2 corrected--Log Lx for PC 1000+4751 from 44.0 (incorrect) to 45.0 (correct). A few minor errors corrected
dc.identifierhttps://arxiv.org/abs/astro-ph/0510257
dc.identifierhttp://arxiv.org/abs/astro-ph/0510257
dc.identifierAstron.J.131:659-665,2006
dc.identifierdoi:10.1086/498717
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/195324
dc.subjectAstrophysics
dc.titleChandra Observations of Six QSOs at z $\approx$ 3
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