The X-ray emission of the most luminous 3CR radio sources

TL;DR

This study examines the X-ray properties of the most luminous 3CR radio sources to compare their emission characteristics with radio-quiet quasars, revealing differences in spectral indices and absorption effects.

Contribution

It provides new X-ray observations of the most luminous 3CR radio sources and analyzes their spectral properties, highlighting differences between type 1 and type 2 sources and implications for jet-related emission.

Findings

Type 1 sources have flatter alphaox than radio quiet quasars.

Type 2 sources show lower absorption-corrected X-ray luminosity, aligning with radio quiet quasars.

Compton thick objects exhibit a more luminous reflected component.

Abstract

We investigate the X-ray properties of the most luminous radio sources in the 3CR catalogue, in order to assess if they are similar to the most luminous radio quiet quasars, for instance in the X-ray normalization with respect to the optical luminosity, or in the distribution of the absorption column density. We have selected the (optically identified) 3CR radio sources whose 178-MHz monochromatic luminosity lies in the highest factor-of-three bin. The 4 most luminous objects had already been observed in X rays. Of the remaining 16, we observed with XMM-Newton 4 randomly chosen, optical type 1s, and 4 type 2s. All targets have been detected. The optical-to-Xray spectral index, alphaox, can be computed only for the type 1s and, in agreement with previous studies, is found to be flatter than in radio quiet quasars of similar luminosity. However, the Compton thin type 2s have an absorption corrected X-ray luminosity systematically lower than the type 1s, by a factor which makes them consistent with the radio quiet alphaox. Within the limited statistics, the Compton thick objects seem to have a reflected component more luminous than the Compton thin ones. The extra X-ray component observed in type 1 radio loud quasars is beamed for intrinsic causes, and is not collimated by the absorbing torus as is the case for the (intrinsically isotropic) disk emission. The extra component can be associated with a relativistic outflow, provided that the flow opening angle and the Doppler beaming factor are 1/5 - 1/7 radians.