The southern molecular environment of SNR G18.8+0.3

摘要

Aims. In a previous paper we investigated the molecular environment toward the eastern border of the supernova remnant (SNR) G18.8+0.3. Continuing with the study of the surroundings of this SNR, we now focus on its southern border, which in the radio continuum emission shows a very peculiar morphology with a corrugated corner and a very flattened southern flank. Methods. We observed two regions toward the south of SNR G18.8+0.3 using the Atacama Submillimeter Telescope Experiment (ASTE) in the 12CO J = 3?2. One of these regions was also surveyed in 13CO and C18O J = 3?2. The angular and spectral resolution of these observations were 22′′ and 0.11 km?s-1. We compared the CO emission to 20 cm radio continuum maps obtained as part of the Multi-Array Galactic Plane Imaging Survey (MAGPIS) and 870 μm dust emission extracted from the APEX Telescope Large Area Survey of the Galaxy. Results. We discovered a molecular feature with a good morphological correspondence with the SNR’s southernmost corner. In particular, there are indentations in the radio continuum map that are complemented by protrusions in the molecular CO image, strongly suggesting that the SNR shock is interacting with a molecular cloud. Toward this region we find that the 12CO peak is not correlated with the observed 13CO peaks, which are likely to be related to a nearby Hii region. Regarding the most flattened border of SNR G18.8+0.3, where an interaction of the SNR with dense material was previously suggested, our 12CO J = 3?2 map shows no obvious indication that this is occurring.