The southern molecular environment of SNR G18.8+0.3

Abstract

In a previous paper we have investigated the molecular environment towardsthe eastern border of the SNR G18.8+0.3. Continuing with the study of thesurroundings of this SNR, in this work we focus on its southern border, whichin the radio continuum emission shows a very peculiar morphology with acorrugated corner and a very flattened southern flank. We observed two regionstowards the south of SNR G18.8+0.3 using the Atacama Submillimeter TelescopeExperiment (ASTE) in the 12CO J=3-2. One of these regions was also surveyed in13CO and C18O J=3-2. The angular and spectral resolution of these observationswere 22", and 0.11 km/s. We compared the CO emission to 20 cm radio continuummaps obtain as part of the Multi-Array Galactic Plane Imaging Survey (MAGPIS)and 870 um dust emission extracted from the APEX Telescope Large Area Survey ofthe Galaxy. We discovered a molecular feature with a good morphologicalcorrespondence with the SNR´s southernmost corner. In particular, there areindentations in the radio continuum map that are complemented by protrusions inthe molecular CO image, strongly suggesting that the SNR shock is interactingwith a molecular cloud. Towards this region we found that the 12CO peak is notcorrelated with the observed 13CO peaks, which are likely related to a nearby Hii region. Regarding the most flattened border of SNR G18.8+0.3, where aninteraction of the SNR with dense material was previously suggested, our 12COJ=3-2 map show no obvious indication that this is occurring.