Aperture synthesis imaging of a high-velocity compact cloud near the galactic center

Abstract

We observed CO J = 1-0 and HCN J = 1-0 line emission toward a high-velocity, compact molecular cloud, CO 0.02-0.02, near the center of our Galaxy, using the Nobeyama Millimeter Array (NMA). A CO velocity-integrated map with a resolution of 4.″3 × 2.″4 shows two oval clumps with sizes of 0.8 pc. These clumps are seperated by 1.2 pc, being located at the eastern and southwestern peripheries of the CO 0.02-0.02 cloud. The overall distribution of HCN emission coincides with that taken with the Nobeyama 45 m telescope. The HCN velocity-integrated map with a resolution of 6.″ × 3.″4 shows two prominent peaks in the cloud center. Both NMA maps at VLSR ∼ 110km s-1 show an arc-shaped edge in the southeast, which may correspond to the edge of the "emission cavity" found in the CO J = 3-2 integrated-intesity map. We also noticed a faint radio continuum "arc" that encircles the bulk of the CO 0.02-0.02 cloud. These results support the notion that CO 0.02-0.02 has been accelerated, heated, and compressed in a series of supernova shocks that occurred within the last (3-5) × 104 yr. We suggest that a massive compact cluster with an age of 10-30 Myr is responsible for the formation of the CO 0.02-0.02 cloud. © 2008. Astronomical Society of Japan.