The hard X-ray view of Giga-Hertz Peaked Spectrum Radio Galaxies
Abstract
We present the first broadband X-ray observations of 4 Giga-Hertz Peaked Spectrum (GPS) radio galaxies at redshift 2 keV) X-rays. All sources were detected. Their radio-to-X-ray spectral energy distributions are similar, except for PKS0941-080, which is by about two orders of magnitude X-ray under-luminous. The comparison between the full sample of GPS galaxies with measurements in hard X-rays and a control sample of radio galaxies rules out intrinsic X-ray weakness as an origin for the lower detection rate of GPS sources in X-ray surveys. 4 out of 7 GPS galaxies exhibit large X-ray column densities, whereas for the remaining 3 this measurement is hampered by the poor spectral statistics. Bearing in mind the still low number statistics in both the GPS and the control sample, the average column density measured in GPS galaxies is larger than in FRI or Broad Line Region FRII radio galaxies, but consistent with that measured in High-Excitation FRII galaxies. This leads to locating the absorbing gas in an obscuring "torus", which prevents us from observing the nuclear region along lines-of-sight perpendicular to the radio axis. This interpretation is supported by the discovery of rapid (timescale \~1000 s) X-ray variability in COINSJ0029+3456, and by an almost order-of-magnitude difference between the HI column density measured in radio and X-rays in PKS0500+019.Keywords
All Related Versions
This publication has 0 references indexed in Scilit: