Models of Stephan’s Quintet: Hydrodynamic Constraints on the Group’s Evolution

We present smoothed particle hydrodynamic models of the interactions in the compact galaxy group, Stephan’s Quintet. This work is extension of the earlier collisionless N-body simula-tions of Renaud et al. in which the large-scale stellar morphology of the group was modeled with a series of galaxy-galaxy interactions in the simulations. Including thermohydrodynamic effects in this work, we further investigate the dynamical interaction history and evolution of the intergalactic gas of Stephan’s Quintet. The major features of the group, such as the ex-tended tidal features and the group-wide shock, enabled us to constrain the models reasonably well, while trying to reproduce multiple features of the system. We found that reconstructing the two long tails extending from NGC 7319 toward NGC 7320c one after the other in two separate encounters is very difficult and unlikely, because the second encounter usually de-stroys or distorts the already-generated tidal structure. Our models suggest the two long tails may be formed simultaneously from a single encounter between NGC 7319 and 7320c, result-ing in a thinner and denser inner tail than the outer one. The tails then also run parallel to each other as observed. The model results support the ideas that the group-wide shock detected i