Outlined is the discovery of a very faint, diffuse, low surface-brightness (0.5 mJy beam −1 , 1.4 mJy arcmin −2 on average) structure around the radio source B2 0258+35 hosted by an HI-rich early-type galaxy (NGC 1167). Because B2 0258+35 is a young compact steep spectrum (CSS) source, the newly discovered structure could represent a remnant from an earlier stage of activity of an active galactic nucleus (AGN). We explain in detail all possibilities for triggering the radio activity in B2 0258+35 regarding gas accretion in a recurrent AGN activity framework. NGC 1167 hosts a very regular, extended and massive H I disk that has been studied in great detail. It has regular kinematics on large scales, which, together with stellar population studies of NGC 1167, exclude the possibility of a recent merger as the trigger for the current AGN activity that is responsible for the CSS source. Previous studies of the H I closer to the core seem to preclude the assumption of a circum-nuclear disk of H I as the source of the accreting gas. We consider the cooling of gas from the hot X-ray halo as a possible alternative option for the fueling of the AGN, as suggested for other sources of similar radio power as B2 0258+35. This would provide a more likely explanation for the recurrent activity. Furthermore, if the previously made suggestion in the literature that the inner CSS may not be able to grow to large scales is correct, this implies that different cycles of activity may have different characteristics (e.g. radio power of the emission). Estimates are given for the age of the faint diffuse emission as well as for the current accretion rate, which agree well with literature values. If our assumptions about the accretion mechanism are correct, similar large-scale, relic-like structures should be more commonly found around early-type galaxies, which will hopefully be confirmed by the next generation of sensitive, low-frequency radio surveys.

We present new ATCA 21-cm line observations of the neutral hydrogen in the nearby radio galaxy Centaurus A. We image in detail (with a resolution down to 7 , ∼100 pc) the distribution of H i along the dust lane. Our data have better velocity resolution and better sensitivity than previous observations. The H i extends for a total of ∼15 kpc. The data, combined with a titled-ring model of the disk, allow to conclude that the kinematics of the H i is that of a regularly rotating, highly warped structure down to the nuclear scale.The parameters (in particular the inclination) of our model are somewhat different from some of the previously proposed models but consistent with what was recently derived from stellar light in a central ring. The model nicely describes also the morphology of the dust lane as observed with Spitzer. There are no indications that large-scale anomalies in the kinematics exist that could be related to supplying material for the AGN. Large-scale radial motions do exist, but these are only present at larger radii (r > 6 kpc). This unsettled gas is mainly part of a tail/arm like structure. The relatively regular kinematics of the gas in this structure suggests that it is in the process of settling down into the main disk. The presence of this structure further supports the merger/interaction origin of the H i in Cen A. From the structure and kinematics we estimate a timescale of 1.6−3.2 × 10 8 yr since the merging event. No bar structure is needed to describe the kinematics of the H i. The comparison of the timescale derived from the large-scale H i structure and those of the radio structure together with the relative regularity of the H i down to the sub-kpc regions does not suggest a oneto-one correspondence between the merger and the phase of radio activity. Interestingly, the radial motions of the outer regions are such that the projected velocities are redshifted compared to the regular orbits. This means that the blueshifted absorption discovered earlier and discussed in our previous paper cannot be caused by out-moving gas at large radius projected onto the centre. Therefore, the interpretation of the blueshifted absorption, together with at least a fraction of the redshifted nuclear absorption, as evidence for a regular inner disk, still holds. Finally, we also report the discovery of two unresolved clouds detected at 5.2 and 11 kpc away (in projection) from the H i disk. They are likely an other example of a left-over of the merger that brought the H i gas.

We present a study of the morphology and kinematics of the neutral hydrogen in the gas-rich (M HI = 1.5 × 10 10 M ), massive earlytype galaxy NGC 1167, which was observed with the Westerbork Synthesis Radio Telescope (WSRT). The H i is located in a 160 kpc disk (≈3 × D 25 ) and has low surface density (≤2 M pc −2 ). The disk shows regular rotation for r < 65 kpc but several signs of recent and ongoing interaction and merging with fairly massive companions are observed. No population of cold gas clouds is observed -in contrast to what is found in some spiral galaxies. This suggests that currently the main mechanism bringing in cold gas to the disk is the accretion of fairly massive satellite galaxies, rather than the accretion of a large number of small gas clumps. NGC 1167 is located in a (gas-) rich environment: we detect eight companions with a total H i mass of ∼6 × 10 9 M within a projected distance of 350 kpc. Deep optical images show a disrupted satellite at the northern edge of the H i disk. The observed rotation curve shows a prominent bump of about 50 km s −1 (in the plane of the disk) at r ≈ 1.3 × R 25 . This feature in the rotation curve occurs at the radius where the H i surface density drops significantly and may be due to large-scale streaming motions in the disk. We suspect that both the streaming motions and the H i density distribution are the result of the interaction/accretion with the disrupted satellite. Like in other galaxies with wiggles and bumps in the rotation curve, H i scaling describes the observed rotation curve best. We suggest that interactions create streaming motions and features in the H i density distribution and that this is the reason for the success of H i scaling in fitting such rotation curves.