X-ray observations of low-power FR I radio galaxies

According to unified schemes for Active Galactic Nuclei, low-power, Fanaroff-Riley type I (FR I), radio galaxies are thought to be BL Lacs with their jets pointing at relatively large angles with respect to the line of sight. X-ray observations of FR I sources can test this scenario and constrain the presence of obscuring material around the nucleus. In this paper we discuss the X-ray properties of three FR I radio galaxies 3C 78, OH–342 and PKS 0620–52, observed with the BeppoSAX satellite in the 0.2–10 keV energy range. The narrow-field instruments on board BeppoSAX have detected extended thermal X-ray emission from a hot galactic corona (3C 78) and intracluster gas (OH–342 and PKS 0620–52). However, a detailed spectral analysis suggests that a non-thermal (likely nuclear) component can also significantly contribute to the total flux, especially in the case of 3C 78 and OH–342. This emission from the central region appears basically unabsorbed, in agreement with observations in other bands. The X-ray spectral luminosity of the nucleus of these three objects is correlated with the radio core luminosity, consistently with previous data on other FR I radio galaxies.