SUBMILLIMETER CONTINUUM EMISSION FROM THE GALACTIC-CENTER REGION

The Galactic Center and surrounding region have been mapped in the con tinuum at 1100, 800, and 450 mum. Apart from Sgr A itself, the emissi on is dominated by warm dust. The 1100 mum map shows four distinct gia nt molecular clouds (GMCs) with complex multiple cores. In addition, a weaker ridge follows the Galactic plane, and appears to link up the G MCs. Beyond this ridge, particularly toward positive latitudes, the du st emission drops rapidly below the detection limit. A 14'' resolution 800 mum map of the region shows the central 2 pc ring, with two brigh t clumps corresponding with the peaks seen in HCN. Two thin lines of e mission appear to link the southern GMC M -0.13-0.08 with the 2 pc rin g; the points of intersection correspond with the densest molecular cl umps and H-2 ''hot spots'' in the ring. We suggest that these may be s tream lines along which gas and dust are flowing onto the central ring . The continuum emission to the east of Sgr A appears to form an almo st complete oval shell, whose easternmost boundary is the cloud M-0.02 -0.07, and whose western side is coincident with the 2 pc ring. This s tructure shows remarkable agreement with published maps of synchrotron radio emission, suggesting that much of M-0.02-0.07 is externally hea ted by a single source. The luminosity of M-0.02-0.07 is almost-equal- to 3 x 10(7) L. which implies that if the energy source is isotropic a nd lies near Sgr A, a total luminosity of approximately 10(9) L. is r equired. Molecular gas from the northwest section of this shell was ma pped in J = 3-2 (CO)-C-12 and agrees closely with the dust images. The re is evidence of a strong velocity gradient as the gas nears the 2 pc ring, which would imply close proximity to Sgr A. It follows that th e whole of this shell, including Sgr A East, must lie close to Sgr A. The 7'' resolution 450 mum map of the central 2' shows the southwest and northeast sectors of the 2 pc ring. However, little emission is de tected from the region of the anomalous velocity cloud previously seen in HCN to the northwest of Sgr A (Gusten et al. 1987). We suggest th at this may be a cooler cloud lying along the line of sight, and not a n integral part of the ring. With this assumption, the morphology of r adio continuum emission, in particular the north and south ''spiral ar ms'' appears to be determined mainly by the shape of the dust arcs mak ing up the incomplete ring. The east and west radio arms have no corre sponding dust components, so their morphology may be determined in som e other way.