Interaction between the W51C Supernova Remnant and a Molecular Cloud. I. H I 21 Centimeter Line Observations
Abstract
We report the results of high-resolution H I 21 cm line observations of the shocked interstellar gas in the W51 complex. The shocked H I gas has been detected between vLSR ~= +85 and +180 km s-1, which is much greater than the maximum velocity (~60 km s-1) permitted by the Galactic rotation toward this direction (l = 49°). The H I gas is distributed along a looplike filamentary structure of ~20' × ~3' size (or ~35 pc × ~5 pc at a distance of 6 kpc). The velocity structure indicates that the H I gas is a portion of an expanding, concave shell. By comparing with the X-ray/CO distributions, we have found that the shocked H I gas is located at an interface between the X-ray-bright central region of the W51C supernova remnant (SNR) and a large molecular cloud. The correlation between the X-ray, CO, and H I emissions strongly suggests that a shock driven by the SNR is propagating into the molecular cloud. The large amount (>1200 M⊙) of fast-moving H I gas indicates that the shock is a fast, radiative, J-type shock. The VLA line profiles yield a maximum line-of-sight shock velocity of ~=70 km s-1. A simple model in which a hemispherical H I shell is expanding into a cylindrical cloud from the side could explain the observed morphology and velocity structure of the H I gas. The shock velocity corrected for the projection is ~100 km s-1. We derive the shock parameters and discuss the implications for the SNR W51C.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 1997
- DOI:
- 10.1086/303527
- Bibcode:
- 1997ApJ...475..194K
- Keywords:
-
- ISM: Clouds;
- ISM: Individual: Alphanumeric: W51;
- Radio Lines: ISM;
- Shock Waves;
- ISM: Supernova Remnants