Molecular environment and thermal X-ray spectroscopy of the semicircular young composite supernova remnant 3C 396

TL;DR

This study investigates the molecular environment and X-ray properties of supernova remnant 3C 396, revealing interactions with molecular clouds, estimating the remnant's age at around 3,000 years, and suggesting a B1-B2 progenitor star.

Contribution

It provides new insights into the molecular interactions and thermal X-ray characteristics of 3C 396, identifying specific molecular cloud interactions and estimating the remnant's age and progenitor type.

Findings

Molecular clouds at V(LSR)~84km/s interact with the SNR.

The SNR is approximately 3,000 years old.

The progenitor star was likely a 13-15Msun B1-B2 star.

Abstract

We have investigated the molecular environment of the semicircular composite supernova remnant (SNR) 3C396 and performed a Chandra spatially resolved thermal X-ray spectroscopic study of this young SNR. With our CO millimeter observations, we find that the molecular clouds (MCs) at V(LSR)~84km/s can better explain the multiwavelength properties of the remnant than the V(LSR)=67-72km/s MCs that are suggested by Lee et al. (2009). At around 84km/s, the western boundary of the SNR is perfectly confined by the western molecular wall. The CO emission fades out from west to east, indicating that the eastern region is of low gas density. In particular, an intruding finger/pillar-like MC, which may be shocked at the tip, can well explain the X-ray and radio enhancement in the southwest and some infrared filaments there. The SNR-MC interaction is also favored by the relatively elevated 12CO J=2-1/J=1-0 line ratios in the southwestern "pillar tip" and the molecular patch on the northwestern boundary. The redshifted 12CO (J=1-0 and J=2-1) wings (86-90km/s) of an eastern 81km/s molecular patch may be the kinematic evidence for shock-MC interaction. We suggest that the 69km/s MCs are in the foreground based on HI self-absorption while the 84km/s MCs at a distance of 6.2 kpc (the tangent point) are in physical contact with SNR 3C396. The X-ray spectral analysis suggests an SNR age of ~3kyr. The metal enrichment of the X-ray emitting gas in the north and south implies a 13-15Msun B1-B2 progenitor star.