CO Observations of the Type Ia Supernova Remnant 3C 397 by the Nobeyama 45-m Radio Telescope: Possible Evidence for the Single-Degenerated Explosion

TL;DR

This study uses high-resolution CO observations to link the supernova remnant 3C 397 with a specific molecular cloud, providing evidence supporting a single-degenerate explosion scenario involving pre-supernova wind feedback.

Contribution

First high-resolution CO mapping of 3C 397 reveals its association with a specific molecular cloud, supporting the single-degenerate supernova explosion model.

Findings

Identified a 60 km/s CO cloud spatially associated with 3C 397.

Detected an expanding gas motion in the cloud with ~3 km/s velocity.

Supported the single-degenerate explosion scenario through wind-blown bubble evidence.

Abstract

We present a new CO observation toward the Type Ia supernova remnant (SNR) 3C 397 using the Nobeyama 45-m radio telescope at an unprecedent angular resolution of $\sim$18''. We newly found that the CO cloud at $V_{\mathrm{LSR}}$ = 55.7-62.2 km s$^{-1}$ (60 km s$^{-1}$ cloud) shows a good spatial correspondence with the radio continuum shell. We also found an expanding gas motion of the 60 km s$^{-1}$ cloud with an expansion velocity of $\sim$3 km s$^{-1}$, which is thought to be formed by the pre-and/or post-supernova feedback. By considering the positions of Galactic spiral arms and the X-ray/HI absorption studies, we concluded that 3C 397 is physically associated with the 60 km s$^{-1}$ cloud rather than the previously known CO cloud at $V_{\mathrm{LSR}}$ $\sim$30 km s$^{-1}$. Given that the previously measured pre-shock density is $\sim$2-5 cm$^{-3}$, the expanding motion of the 60 km s$^{-1}$ cloud was likely formed by the pre-supernova feedback known as optically thick wind. The scenario is consistent with that 3C 397 exploded inside a wind-blown bubble as a single degenerate system.