A FURTHER STUDY OF THE MOLECULAR CLOUD ASSOCIATED WITH THE SUPERNOVA REMNANT G109.1-1.0

The region of the semicircular supernova remnant G109.1-1.0 (CTB 109) is studied on the basis of CO observations with the Nobeyama Radio Observatory (NRO) 45 m radio telescope and X-ray data from the archive of the Einstein Observatory. By observing the J = 1-0 transition of CO at 115 GHz, the distribution of the molecular cloud associated with the remnant is investigated in detail. The resolution of the CO mapping observations is 30″-60″ (0.6-1.2 pc), and the number of the CO spectra obtained is about 2000. The molecular ridge (CO arm), which was known to show an apparent anticorrelation with the curled X-ray jetlike feature of the remnant, is resolved into two CO filaments. X-ray spectra toward the CO arm are harder than those toward the surrounding region. The harder X-ray spectrum, together with the decrease of the X-ray intensity, suggests that X-ray absorption takes place, although there remains a possibility that hotter plasma is located along the line of sight toward the CO arm by chance. The hardness of the X-ray spectrum toward the CO arm is consistent with the column densities of the two CO filaments. However, the overall appearance of the remnant will not be affected very much by the absorption, because the X-ray absorption is found to be a minor effect. Shock-accelerated CO gas has not been observed toward the G109.1-1.0 region. The upper bound to the intensity of shock-accelerated CO gas is 0.4 K for the whole mapped region, and the upper bound toward 11 points observed at a lower noise level is 0.1 K. These upper bounds are below the intensity (1-2 K) of shock-accelerated CO gas associated with IC 443.