The HI and ionized gas disk of the Seyfert galaxy NGC 1144=Arp 118: A violently interacting galaxy with peculiar kinematics

We present observations of the distribution and kinematics of neutral and i onized gas in NGC 1144, a galaxy that forms part of the Arp 118 system. Ion ized gas is present over a huge spread in velocity (1100 km s(-1)) in the d isk of NGC 1144, but H I emission is detected over only one-third of this v elocity range, in an area that corresponds to the NW half of the disk. In t he nuclear region of NGC 1144, a jump in velocity in the ionized gas compon ent of 600 km s(-1) is observed. Faint, narrow H I absorption lines are als o detected against radio sources in the SE part of the disk of NGC 1144, wh ich includes regions of massive star formation and a Seyfert nucleus. The p eculiar H I distribution, which is concentrated in the NW disk, seems to be the inverse of the molecular distribution that is concentrated in the SE d isk. Although this may partly be the result of the destruction of H I cloud s in the SE disk, there is circumstantial evidence that the entire H I emis sion spectrum of NGC 1144 is affected by a deep nuclear absorption line cov ering a range of 600 km s(-1) and is likely blueshifted with respect to the nucleus. In this picture, a high column density H I stream is associated w ith the nuclear ionized gas velocity discontinuity, and the absorption effe ctively masks any H I emission that would be present in the SE disk of NGC 1144.