Astronomy and Astrophysics – Astrophysics
Scientific paper
2003-02-20
Astron.Astrophys.402:465-476,2003
Astronomy and Astrophysics
Astrophysics
13 pages, 11 figures, accepted for publication in A&A
Scientific paper
10.1051/0004-6361:20030275
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 (\Gamma \la 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 (\Gamma \sim 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 Ly$\alpha $ system (N(HI)\sim 2.6\times 10^{21} cm^{-2} at z = 3.39) cannot be examined further due to the limited photon statistics in all instruments.
Brinkmann Wolfgang
Ferrero Elisa
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