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Is HCG31 undergoing a merger or a fly-by interaction?

M. G. Richer·L. Georgiev·M. Rosado·A. Bullejos·M. Valdez-Gutierrez·D. Dultzin-Hacyan
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Abstract

We present Fabry-Perot and multi-object spectroscopy of the galaxies in Hickson compact group 31 (HCG31). Based upon our H$α$ 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 5$ $mag. 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 \ion{H}{i} 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 HCG31. In this case, the A+C complex need not be a merger in progress, though this is not ruled out.

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M. G. Richer, L. Georgiev, M. Rosado, A. Bullejos, M. Valdez-Gutierrez, D. Dultzin-Hacyan. 2002-11-03. Is HCG31 undergoing a merger or a fly-by interaction?. https://doi.org/10.1051/0004-6361%3A20021394

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