The Cassiopeia Filament: A Blown Spur of the Local Arm
Abstract
We present wide-field and high-sensitivity CO(1-0) molecular line observations toward the Cassiopeia region, using the 13.7 m millimeter telescope of the Purple Mountain Observatory. The CO observations reveal a large-scale highly filamentary molecular cloud within the Galactic region of 132.°0 ≥ l ≥ 122.°0 and -1.°0 ≤ b ≤ 3.°0 and the velocity range from approximately +1 to +4 km s-1. The measured length of the large-scale filament, referred to as the Cassiopeia Filament, is ~390 pc. The observed properties of the Cassiopeia Filament, such as length, column density, and velocity gradient, are consistent with those synthetic large-scale filaments in the inter-arm regions. Based on its observed properties and location on the Galactic plane, we suggest that the Cassiopeia Filament is a spur of the Local arm, which is formed due to the galactic shear. The western end of the Cassiopeia Filament shows a giant arc-like molecular gas shell, which extends in the velocity range from roughly -1 to +7 km s-1. Finger-like structures, with systematic velocity gradients, are detected in the shell. The CO kinematics suggest that the large shell is expanding at a velocity of ~6.5 km s-1. Both the shell and finger-like structures outline a giant bubble with a radius of ~16 pc, which is likely produced by the stellar wind from the progenitor star of a supernova remnant. The observed spectral line widths suggest that the whole Cassiopeia Filament was quiescent initially until its west part was blown by the stellar wind and became supersonically turbulent.
- Publication:
-
The Astronomical Journal
- Pub Date:
- January 2023
- DOI:
- 10.3847/1538-3881/ac9ea2
- arXiv:
- arXiv:2211.00810
- Bibcode:
- 2023AJ....165...16C
- Keywords:
-
- Interstellar medium;
- Interstellar filaments;
- Giant molecular clouds;
- Stellar wind bubbles;
- 847;
- 842;
- 653;
- 1635;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 46 pages, 19 figures, to be published by the AJ