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).