부산대학교 도서관

We present CO(3-2), CO(2-1), and 230 GHz (1.3 mm) continuum images of nearby galaxies takenwith the Submillimeter Array (SMA). Our main topic is to study the relation between higher-J moleculargas (e.g., CO J=3-2, 2-1) and nuclear activities (e.g., active galactic nuclei [AGNs] and starbursts). Thenearby Seyfert 2 galaxy M51 shows strong CO(3-2) emission from the circumnuclear molecular gas, withan intensity twice as strong as that of the CO(1-0) emission. Strong CO(3-2) emission enhancementsuggests that the circumnuclear molecular gas in M51 is warm and dense, which may be related tothe AGN activities. Molecular gas in the nearby moderate starburst galaxy NGC 6946 is distributedalong the large-scale bar or spiral arms and along the minibar, and the multi-J CO line images showvery similar distribution to each other. For this galaxy, there is no clear enhancement in higher-Jlines as seen in M51, which may be because NGC 6946 does not have clear AGN activities. Basedon the results of these two galaxies, the physical conditions of the circumnuclear molecular gas maybe related to the AGN activities. We also observed the nearby edge-on starburst galaxy NGC 3628and the starburst/Seyfert composite galaxy NGC 4945 with the CO(2-1) line and 230 GHz (1.3 mm)continuum emission. These information will give us some hints for understanding the relation betweennuclear activities and circumnuclear molecular gas and dust.