Ammonia Emission from Bow Shocks in the L1157 Outflow
Abstract
We present high-resolution (approximately = 5 arcsecs) NH3 (1, 1) and NH3 (3, 3) observations toward the blue lobe of the remarkable bipolar outflow L1157. We find that the ammonia emission arises from several compact condensations that are well aligned with IRAS 20386+6751, the origin of the outflow. The gas that emits in ammonia has been strongly affected by the outflow. In addition of having been accelerated, the gas has been heated to temperatures of more than 60-80 K (a factor of 5 with respect to its quiescent value), and its ammonia abundance has been enhanced by more than an order of magnitude. We interpret the ammonia emission as arising from a series of bow shocks along the outflow axis, and although we cannot detect the shocking agent, our observations suggest that it is in the form of a highly collimated jet. The multiplicity of the ammonia peaks along the outflow suggests the jet is episodic, and the emitting source is so reddened, that most likely represents a case of a Class 0 object.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1995
- DOI:
- 10.1086/187830
- Bibcode:
- 1995ApJ...443L..37T
- Keywords:
-
- Ammonia;
- Bipolarity;
- Gas Flow;
- Molecular Spectroscopy;
- Shock Waves;
- Stellar Envelopes;
- Abundance;
- Emission Spectra;
- Gas Dynamics;
- Stellar Winds;
- Temperature Distribution;
- Velocity Distribution;
- Astronomy;
- ISM: INDIVIDUAL ALPHANUMERIC: L1157;
- ISM: JETS AND OUTFLOWS;
- SHOCK WAVES;
- STARS: FORMATION