Detection of a Thick Molecular Disk in the Galaxy
Abstract
The 1.2 m telescope at the Center for Astrophysics was used to conduct the first sensitivity and systematic search for molecular gas in the inner Galaxy more than 100 pc from the Galactic plane. With an rms sensitivity per spectrum of 0.1 K at delta upsilon = 1.3 km/s and a sampling interval of 3.75 min (0.43 beamwidth), the survey is 3-10 times more sensitive per unit solid angle than existing CO surveys of the plane, and 16 times more sensitive than the only previous extensive wide-latitude survey. Three selected regions centered on the planed were mapped, each approx. 1 deg wide in l and approx. 8 deg wide in b, at Galactic longitudes 30 deg, 40 deg, and 50 deg; in all three there is CO emission near the terminal velocity extending up to 3 deg from the plane. This CO is evidence for a faint, thick molecular disk in the inner Galaxy approx. 3 times as wide as that of the dense central CO layer, and comparable in width to the central H I layer. In the inner Galaxy regions surveyed, approx. 5% of the total emission, and possibly a comparable fraction of the H2 mass, lies above the previously studied thin molecular disk.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1994
- DOI:
- 10.1086/187660
- Bibcode:
- 1994ApJ...436L.173D
- Keywords:
-
- Galactic Halos;
- Galactic Structure;
- Interstellar Gas;
- Milky Way Galaxy;
- Molecular Gases;
- Carbon Monoxide;
- Normal Density Functions;
- Optical Thickness;
- Space Density;
- Telescopes;
- Velocity;
- Astrophysics;
- ISM: MOLECULES;
- ISM: STRUCTURE;
- GALAXY: STRUCTURE;
- GALAXY: HALO