Extended Ionized Gas Emission and Kinematics of the Compact Group Galaxies in Hickson Compact Group 16: Signatures of Mergers

We report on kinematic observations of Ha emission line from four late-typegalaxies of Hickson Compact Group 16 (H16a,b,c and d) obtained with a scanningFabry-Perot interferometer and samplings of 16 km/s and 1". The velocity fieldsshow kinematic peculiarities for three of the four galaxies: H16b, c and d.Misalignments between the kinematic and photometric axes of gas and stellarcomponents (H16b,c,d), double gas systems (H16c) and severe warping of thekinematic major axis (H16b and c) were some of the peculiarities detected. Weconclude that major merger events have taken place in at least two of thegalaxies group. H16c and d, based on their significant kinematic peculiarities,their double nuclei and high infrared luminosities. Their Ha gas content isstrongly spatially concentred - H16d contains a peculiar bar-like structureconfined to the inner $\sim$ 1 h^-1 kpc region. These observations are inagreement with predictions of simulations, namely that the gas flows towardsthe galaxy nucleus during mergers, forms bars and fuel the central activity.Galaxy H16b, and Sb galaxy, also presents some of the kinematic evidences forpast accretion events. Its gas content, however, is very spare, limiting ourability to find other kinematic merging indicators, if they are present. Wefind that isolated mergers, i.e., they show an anormorphous morphology and nosigns of tidal tails. Tidal arms and tails formed during the mergers may havebeen stripped by the group potential (Barnes & Hernquist 1992) ar alternativelythey may have never been formed. Our observations suggest that HCG 16 may be ayoung compact group in formation throught the merging of close-by objects in adense environment.Comment: Accepted for publication in ApJ. 35 pages, 13 figures. tar file gzipped and uuencode