A Multiwavelength Study of Stephan’s Quintet

Abstract

Stephan's Quintet (SQ) is a compact group that we find in an atypical moment when a high velocity intruder is passing through it. The intrusion is particularly interesting because a previous intruder had stripped most of the gas from the group members. This debris field was shocked in the ongoing collision with the new intruder. This evolutionary history agrees well with observations and explains how a strongly interacting system can show low levels of star formation. We present new multiwavelength data including previously unpublished ROSAT X-ray, Ha interference filter/FP, ISO MIR/FIR and radio line and continuum images. These observations and previously published data provide new insights as well as support for some previous hypotheses. 1) FP and HI velocities allow us to unambiguously distinguish between gas associated with SQ and the new intruder. 2) Most detected emission regions are found in the remnant ISM of the NI which allows us to infer its size and present physical state. 3) The few emission regions associated with the stripped ISM of SQ include the best candidate tidal dwarf galaxy. 4) Multiwavelength data suggest that strong MIR/FIR emission from the Seyfert 2 nucleus of NGC7319 comes from dust heated directly by a power-law continuum rather than a starburst. 5) The correspondance between extended X-ray/radio continuum/forbidden optical emission confirms the existence of a large scale shock in SQ.