A MASSIVE COMETARY CLOUD ASSOCIATED WITH IC 1805

摘要

High-resolution, wide field imaging of ~(12)CO, 21 cm line and continuum, and IRAS far-infrared emissions from the outer Galaxy have identified a massive cometary molecular cloud associated with IC 1805. The dense cloud is remnant molecular material within a large 10~2 pc cavity evacuated by the stellar winds and UV radiation field of the cluster O stars. A 37 pc long molecular tail points directly away from the sources of ionizing radiation and is likely due to the effective shielding of radiation by the dense gas and associated dust within the cometary head region. Maps of C~(18)O J = 1-0 and CS J = 2-1 emissions are presented that constrain the column and mean volume densities within the cometary head region to 10~(22) cm~(-2) and 10~4 cm~(-3), respectively. A 1155 solar luminosity point source embedded within the dense gas of the cometary head region provides evidence for ongoing star formation that may have been triggered by shocks driven by the ionization front.