Widespread Water Vapor Emission in Orion
Abstract
We have discovered spatially extended emission in the 313 - 220 line of water vapor in Orion. This is the first time that extended water emission has been found in the interstellar medium. Many strong narrow features with flux density approx. (1 - 15) x 103 Jy have been detected around Ori A-IRc2. These features appear superposed over a weaker (approx. 103 Jy high velocity plateau with a half-power size of approx. equals 45 sec, and a total extent of 80 sec x 80 sec. Narrow lines with intensities approx. 25 - 200 Jy, are detected at the velocity of the molecular cloud for all the positions observed along the molecular ridge. These lines are not arising from point sources and the different emission regions are well resolved by our 15 sec beam. Narrow and blueshifted emission is also found along a filament containing the S6 source 100 sec south of IRc2. From statistical equilibrium and radiative transfer calculations for the physical conditions of the Orion molecular cloud, we conclude that the nature of the observed water vapor emission is dominated by maser emission. The water abundance is estimated to be larger than 10-5, implying that water vapor is a substantial component of the gas phase in warm molecular clouds and one of its most important gas coolants.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1994
- DOI:
- 10.1086/187511
- Bibcode:
- 1994ApJ...432L..59C
- Keywords:
-
- Emission Spectra;
- Interstellar Matter;
- Masers;
- Molecular Clouds;
- Orion Constellation;
- Water Vapor;
- Astronomical Models;
- Flux Density;
- Radiative Transfer;
- Vapor Phases;
- Velocity;
- Astrophysics;
- COSMOLOGY: EARLY UNIVERSE;
- NUCLEAR REACTIONS;
- NUCLEOSYNTHESIS;
- ABUNDANCES;
- STARS: ABUNDANCES;
- STARS: INTERIORS