Astronomy and Astrophysics, volume 397, 99-107 (2003/1-1)
Is HCG 31 undergoing a merger or a fly-by interaction?
RICHER M.G., GEORGIEV L., ROSADO M., BULLEJOS A., VALDEZ-GUTIERREZ M. and DULTZIN-HACYAN D.
Abstract (from CDS):
We present Fabry-Perot and multi-object spectroscopy of the galaxies in Hickson compact group 31 (HCG 31). Based upon our Hα data cubes, galaxies A and C are a single entity, showing no discontinuity in their kinematics. Kinematically, galaxy E is probably a component of the A+C complex; otherwise it is a recently detached fragment. Galaxy F appears, both kinematically and chemically, to have formed from material tidally removed from the A+C complex. Galaxies B and G are kinematically distinct from this complex. Galaxy Q also has a radial velocity compatible with group membership. Galaxies A, B, C, and F have nearly identical oxygen abundances, despite spanning a luminosity range of 5mag. Galaxy B's oxygen abundance is normal for its luminosity, while galaxy F's abundance is that expected given its origin as a tidal fragment of the A+C complex. The oxygen abundances in galaxies A and C are also understandable if the A+C complex is a late-type spiral suffering strong gas inflow and star formation as a result of a tidal interaction. Given the kinematics of both the galaxies and the HI gas, the oxygen abundances, and the position of galaxy G, we propose that an interaction of galaxy G with the A+C complex, rather than a merger of galaxies A and C, is a more complete explanation for the tidal features and other properties of HCG 31. In this case, the A+C complex need not be a merger in progress, though this is not ruled out.
galaxies: abundances - galaxies: evolution - galaxies: formation - galaxies: individual: NGC 1741 - galaxies: clusters: individual: HCG 31
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