Searching for intergalactic star forming regions in Stephan’s Quintet with SITELLE: II. Physical properties and metallicity

Based on SITELLE spectroscopy data, we studied the ionised gas emission for the 175 H α emission regions in the Stephan’s Quintet (SQ). In this paper we perform a detailed analysis of the star formation rate (SFR), oxygen abundance, and nitrogen-to-oxygen abundance ratio (N/O) of the SQ regions, with the intention of exploring the provenance and evolution of this complex structure. According to the BPT diagram, we found 91 HII, 17 composite, and 7 active galactic nucleus-like regions in SQ. Several regions are compatible with fast shocks models without a precursor for solar metallicity and low density ( n = 0.1 cm −3 ), with velocities in the range of 175–300 km s −1 . We derived the total SFR in SQ (log(SFR/ M ⊙ yr −1 = 0.496)). Twenty-eight percent of the total SFR in SQ comes from starburst A, while 9% is in starburst B, and 45% comes from the regions with a radial velocity lower than 6160 km s −1 . For this reason, we assume that the material prior to the collision with the new intruder does not show a high SFR, and therefore SQ was apparently quenched. When considering the integrated SFR for the whole SQ and the new intruder, we found that both zones have a SFR consistent with those obtained in the SDSS star-forming galaxies. At least two chemically different gas components cohabit in SQ where, on average, the regions with high radial velocities ( v > 6160 km s −1 ) have lower values of oxygen abundance and N/O than those with low radial velocities ( v ≤ 6160 km s −1 ). The values found for the line ratios considered in this study, as well as in the oxygen abundance and N/O for the southern debris region and the northernmost tidal tail, are compatible with regions belonging to the outer part of the galaxies. We highlight the presence of inner-outer variation for metallicity and some emission line ratios along the new intruder strands and the young tidal tail south strand. Finally, the SQ H α regions are outside the galaxies because the interactions have dispersed the gas to the peripheral zones.