Interstellar MgO.
Abstract
A search for interstellar and circumstellar MgO has been made in four microwave rotational transitions, based on new laboratory MODR measurements of the molecular constants. Emission possibly attributable to MgO has been detected in two of the transitions, in Ori(KL) and W51M. A radiative transfer analysis of the MgO results is consistent with the observations in all four transitions for reasonable physical conditions. A parallel analysis has been made for SiO and establishes an abundance ratio MgO/SiO of less than 2(-4) in Ori(KL), less than 1(-2) in other interstellar sources, and less than 6(-3) in three circumstellar envelopes which include both O-rich and C-rich stars. Since Mg/Si is approximately 1 cosmically, it is established that MgO/SiO is much less than Mg/Si. One possible explanation of this result is given in terms of metal-oxide models of interstellar grains. For circumstellar envelopes, equilibrium chemistry appears to explain this result.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1985
- DOI:
- 10.1086/163762
- Bibcode:
- 1985ApJ...299..956T
- Keywords:
-
- Abundance;
- Astronomical Spectroscopy;
- Interstellar Matter;
- Stellar Envelopes;
- Brightness Temperature;
- Line Spectra;
- Magnesium Oxides;
- Millimeter Waves;
- Silicon Oxides;
- Astrophysics