CO in Stephan's Quintet: First Evidence of Molecular Gas in the Intragroup Starburst

Abstract

We present the first interferometric evidence of CO(1-0) emission in the intragroup starburst (IGS) region of HCG~92 (Stephan's Quintet). BIMA's large primary beam covers fully both the IGS region and the dominant group member galaxy Seyfert NGC 7319, as well as partially the intruder galaxy NGC 7318B. CO emission of \(\approxgt 4\sigma\) is detected in all of them. The detection of the CO emission associated with the IGS is further supported by comparisons with observations in other wavebands (e.g., HI, mid-IR, \ha). Assuming the standard conversion factor, 3.6--8.0\(\times 10^8~\Msun\) molecular gas is found to be associated with the IGS. Confining to the region of the CO emission peak, a relatively high star-formation efficiency of 8.6\(\Lsun/\Msun\) is derived for the IGS, which is nearly comparable to that of local starburst galaxies (e.g., M82).