Co in Stephan’s Quintet: First Evidence of Molecular Gas in the Intragroup Starburst

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 fully covers both the IGS region and the dominant group member Seyfert galaxy NGC 7319, as well as partially covering the intruder galaxy NGC 7318B. CO emission of *4 j 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 wave bands (e.g., H i, mid-IR, and Ha). Assuming the standard conversion factor, M, molecular gas is found to be associated with the IGS. By confining ourselves to the 8 (3.6–8.0) # 10 region of the CO emission peak, we find that a relatively high star formation efficiency of 8.6 L,/M, is derived for the IGS, which is nearly comparable to that of local starburst galaxies. The IGS triggering mechanism is also briefly discussed. Subject headings: galaxies: clusters: individual (HCG 92) — galaxies: individual (NGC 7318B, NGC 7319) — galaxies: interactions — galaxies: starburst — infrared: galaxies — intergalactic medium — ISM: molecules