CO J=1-0 and J=2-1 Line Observations of the Molecular Cloud - Blocked Supernova Remnant 3C434.1

TL;DR

This study investigates the interaction between supernova remnant 3C434.1 and a nearby molecular cloud through CO line observations, revealing physical interactions, morphological correlations, and proposing a hydrodynamic model for its asymmetric shape.

Contribution

It provides detailed CO line observations and a hydrodynamic model demonstrating the impact of a molecular cloud on the SNR's morphology and spectral properties.

Findings

Molecular cloud is interacting with the SNR, indicated by high J=2-1 to J=1-0 ratio (~1.6).

The SNR's systemic velocity is -13 km/s, placing it at 3.0 kpc distance.

The asymmetric morphology is explained by interaction with a sheetlike molecular cloud.

Abstract

We present the results of CO emission line observations toward the semicircular Galactic supernova remnant (SNR) 3C434.1 (G94.0+1.0). We mapped an area covering the whole SNR in the 12CO J=1-0 emission line using the Seoul Radio Astronomy Observatory (SRAO) 6-m telescope, and found a large molecular cloud superposed on the faint western part of the SNR. The cloud was elongated along the north-south direction and showed a very good spatial correlation with the radio features of the SNR. We carried out 12CO J=2-1 line observations of this cloud using the K\"{o}lner Observatorium f\"{u}r Sub-Millimeter Astronomie (KOSMA) 3-m telescope and found a region in which the 12CO J=2-1 to J=1-0 ratio was high (~ 1.6). This higher excitation, together with the morphological relation, strongly suggested that the molecular cloud was interacting with the SNR. The systemic velocity of the molecular cloud (-13 km/s) gave a kinematic distance of 3.0 kpc to the SNR-molecular cloud system. We derived the physical parameters of the SNR based on this new distance. We examined the variation of the radio spectral index over the remnant and found that it was flatter in the western part, wherein the SNR was interacting with the molecular cloud. We therefore propose that 3C434.1 is the remnant of a supernova explosion that occurred just outside the boundary of a relatively thin, sheetlike molecular cloud. We present a hydrodynamic model showing that its asymmetric radio morphology can result from its interaction with this blocking molecular cloud.