The acceleration and radiative processes active in low-power radio hotspots are investigated by means of new deep near-infrared ( NIR ) and optical VLT observations , complemented with archival , high-sensitivity VLT , radio VLA and X-ray Chandra data .
For the three studied radio galaxies ( 3C 105 , 3C 195 and 3C 227 ) , we confirm the detection of NIR/optical counterparts of the observed radio hotspots .
We resolve multiple components in 3C 227 West and in 3C 105 South and characterize the diffuse NIR/optical emission of the latter .
We show that the linear size of this component ( \gtrsim 4 kpc ) makes 3C 105 South a compelling case for particles ’ re-acceleration in the post-shock region .
Modeling of the radio-to-X-ray spectral energy distribution ( SED ) of 3C 195 South and 3C 227 W1 gives clues on the origin of the detected X-ray emission .
In the context of inverse Compton models , the peculiarly steep synchrotron curve of 3C 195 South sets constraints on the shape of the radiating particles ’ spectrum that are testable with better knowledge of the SED shape at low ( \lesssim GHz ) radio frequencies and in X-rays .
The X-ray emission of 3C 227 W1 can be explained with an additional synchrotron component originating in compact ( < 100 pc ) regions , such those revealed by radio observations at 22 GHz , provided that efficient particle acceleration ( \gamma \gtrsim 10 ^ { 7 } ) is ongoing .
The emerging picture is that of systems in which different acceleration and radiative processes coexist .