The energetic feedback that is generated by radio jets in active galactic nuclei ( AGNs ) has been suggested to be able to produce fast outflows of atomic hydrogen ( H I ) gas that can be studied in absorption at high spatial resolution .
We have used the Very Large Array ( VLA ) and a global very-long-baseline-interferometry ( VLBI ) array to locate and study in detail the H I outflow discovered with the Westerbork Synthesis Radio Telescope ( WSRT ) in the re-started radio galaxy 3C 236 .
We confirm , from the VLA data , the presence of a blue-shifted wing of the H I with a width of \sim 1000 \mathrm { km s ^ { -1 } } .
This H I outflow is partially recovered by the VLBI observation .
In particular , we detect four clouds with masses of 0.28 \text { - - } 1.5 \times 10 ^ { 4 } M _ { \sun } with VLBI that do not follow the regular rotation of most of the H I .
Three of these clouds are located , in projection , against the nuclear region on scales of \lesssim 40 \mathrm { pc } , while the fourth is co-spatial to the south-east lobe at a projected distance of \sim 270 \mathrm { pc } .
Their velocities are between 150 and 640 \mathrm { km s ^ { -1 } } blue-shifted with respect to the velocity of the disk-related H I .
These findings suggest that the outflow is at least partly formed by clouds , as predicted by some numerical simulations and originates already in the inner ( few tens of pc ) region of the radio galaxy .
Our results indicate that all of the outflow could consist of many clouds with perhaps comparable properties as the ones detected , distributed also at larger radii from the nucleus where the lower brightness of the lobe does not allow us to detect them .
However , we can not rule out the presence of a diffuse component of the outflow .
The fact that 3C 236 is a low excitation radio galaxy , makes it less likely that the optical AGN is able to produce strong radiative winds leaving the radio jet as the main driver for the H I outflow .