An X-ray view of the INTEGRAL/IBIS blazars

作者：Gianni S^*; De Rosa A; Bassani L; Bazzano A; Dean T; Ubertini P

来源：Monthly Notices of the Royal Astronomical Society, 2011, 411(4): 2137-2147.

DOI：10.1111/j.1365-2966.2010.17725.x

• galaxies: active
• quasars: general
• X-rays: galaxies

The aim of this work is a broad-band study, using the INTEGRAL, Swift and XMM-Newton satellites, of a sample of nine blazars (seven flat-spectrum radio quasars and two BL Lacertae objects) with redshift (z) up to about 4. The spectral analysis has shown clear evidence of a flattening of the continuum towards low energies (E < 3 keV observer frame). This behaviour is well reproduced, with both an absorbed power-law model (N-H similar to 1020-1023 cm-2 in the rest frame of the sources) and a broken power-law continuum model (with an energy break below 3 keV in the observer frame). No Compton reflection features, Fe K alpha line or hump at high energies have been detected, with the exception of the source IGR J22517+2218, which shows the presence of a weak iron line. In this paper, we also investigate a possible correlation between the absorption column density N-H and the redshift. We confirm the existence of an N-H-z trend, with the higher absorption at z > 2 for a larger sample compared to previous results. A distribution of N-H and the photon index Gamma is also presented. The hard X-ray data allow us to detect highly absorbed sources (with N-H >= 1023 cm-2 in the rest frame of the source) characterized by a photon-index distribution peaking at harder values (Gamma similar to 1.4) with respect to those obtained with XMM data only (Gamma similar to 2).

• 出版日期2011-3