Aperture synthesis of 1667 MHz OH absorption in the direction of the galactic center

Journal Article · Thu Jan 01 04:00:00 EST 1976 · Astron. Astrophys.; (United States)

OSTI ID:5188155

Biegning, J H

The galactic center radio sources Sgr A and Sgr B2 have been mapped, by an aperture synthesis technique, in the 1667 MHz absorption line of OH. The maps have angular and velocity resolutions of 3.25' and 1.44 km s/sup -1/, and cover the velocity range from -200 to 100 km s/sup -1/. Two dense molecular clouds, with radial velocities of 25 and 45 km s/sup -1/, are observed in the direction of Sgr A. If the observed positional gradients with velocity are caused by a rotation of each cloud, then the minimum gravitational binding mass of each one is a few million solar masses. Alternatively, if the 45 km s/sup -1/ cloud was ejected from the galactic nucleus, the event must have occurred within thelast 2 x 10/sup 5/ years. Fifteen discrete OH condensations are seen in the direction of Sgr B2. Near +60 km s/sup -1/, the maps of opacity imply fluctuations of density and/or OH excitation temperature by factors of about two to four within the cloud, and a possible deficiency of (ground state) OH relative to CO in the molecular core. Clouds detected at negative velocities are small (some possibly unresolved) and have a patchy distribution. If these are associated with an expanding and rotating molecular ring, as has been proposed, then the mass of the ring may be much less than previous estimates. The negative-velocity clouds have, on the average, OH densities and velocity dispersions lower by factors of four and two, than the positive-velocity clouds.

• Research Organization: Max-Planck-Inst. fuer Radioastronomie, Bonn
• OSTI ID: 5188155
• Journal Information: Astron. Astrophys.; (United States), Journal Name: Astron. Astrophys.; (United States) Vol. 51; ISSN AAEJA
• Country of Publication: United States
• Language: English

Related Subjects

640103* -- Astrophysics & Cosmology-- Quasi-Stellar
Radio
& X-Ray Sources-- (-1987)
640105 -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION SPECTRA
AGE ESTIMATION
BINDING ENERGY
CHEMICAL COMPOSITION
COORDINATES
COSMIC GASES
COSMIC RADIO SOURCES
DISTRIBUTION
ENERGY
EXPANSION
FLUIDS
GALAXIES
GASES
GRAVITATIONAL FIELDS
MASS
MILKY WAY
MOTION
ROTATION
SPECTRA
TOPOLOGICAL MAPPING
TRANSFORMATIONS
VELOCITY