What Do theHubble Space TelescopeandChandraTell Us about the Jet and the Nuclear Region of the Radio Galaxy 3C 270?

Abstract

The Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph ultraviolet image of the FR I radio galaxy 3C 270 shows the presence of a jetlike structure emerging from the position of the nucleus. This feature, which represents the first jetlike component ever detected in the UV in a radio galaxy with jets lying almost on the plane of the sky, has the same position angle as the jet in the radio and X-ray images. We propose two different scenarios for the origin of the emission: (1) nonthermal synchrotron from a mildly relativistic component of the jet and (2) scattered light from the nucleus, where a BL Lac source may be hosted. Either of these pictures would have important consequences for the active galactic nuclei unification schemes and for our knowledge of the jet structure. In the Chandra image, a faint counterjet is also present. From a comparative analysis of the HST images and Chandra X-ray spectrum, we find that the nucleus is only moderately obscured. The obscuring structure might well reside in the geometrically thin dark disk observed on large scales. This fits the scenario in which a standard geometrically and optically thick torus is not present in FR I radio galaxies.