Research Note

The southern molecular environment of SNR G18.8+0.3^⋆

¹ Instituto de Astronomía y Física del Espacio (IAFE), CC 67, Suc. 28, 1428 Buenos Aires, Argentina
e-mail: sparon@iafe.uba.ar
² FADU − Universidad de Buenos Aires, Ciudad Universitaria, C1428 EGA Buenos Aires, Argentina
³ CBC − Universidad de Buenos Aires, Ciudad Universitaria, 1053 Buenos Aires, Argentina
⁴ Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile

Received: 8 May 2015
Accepted: 3 July 2015

Abstract

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.