XMM-Newton observations of four high-z quasars

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 × 1021 cm-2 at z = 3.39) cannot be examined further due to the limited photon statistics in all instruments.