Shocks and Star Formation in Stephan's Quintet. I. Gemini Spectroscopy of H{\alpha}-bright knots

Understand

We present a Gemini-GMOS spectroscopic study of HST-selected H{\alpha}-emitting regions in Stephan's Quintet (HCG 92), a nearby compact galaxy group, with the aim of disentangling the processes of shock-induced heating and star formation in its intra-group medium.

• The $\approx$40 sources are distributed across the system, but most densely concentrated in the $\sim$kpc-long shock region.
• Their spectra neatly divide them into narrow- and and broad-line emitters, and we decompose the latter into three or more emission peaks corresponding to spatial elements discernible in HST imaging.
• The emission line ratios of the two populations of H{\alpha}-emitters confirm their nature as H II regions (90% of the sample) or molecular gas heated by a shock-front propagating at $\lesssim$300 km/s.