We present a study of the morphology and kinematics of the neutral hydrogen in the gas-rich ( M _ { HI } = 1.5 \times 10 ^ { 10 } M _ { \odot } ) , massive early-type galaxy NGC 1167 , which was observed with the Westerbork Synthesis Radio Telescope ( WSRT ) .
The H i is located in a 160 kpc disk ( \approx 3 \times D _ { 25 } ) and has low surface density ( \leq 2 M _ { \odot } 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 \sim 6 \times 10 ^ { 9 } M _ { \odot } 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 \approx 1.3 \times 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 .