Molecular gas near the galactic center
The interstellar matter within 400 pc of the center of our Galaxy was studied using millimeter-wave spectroscopy. The region -2/sup 0/.0less than or equal to + 2/sup 0/.0, -0/sup 0/.467 less than or equal to b less than or equal to + 0/sup 0/.467 was surveyed in the lambda = 2.72 mm transition of /sup 13/CO at spacings of 0/sup 0/.067 and 0/sup 0/.133 in l and b respectively. Fourteen distinct kinematic features were identified in the maps of these data; four of the features had not been described before in molecular surveys. Most of the high-velocity features and the nuclear disk are tilted to the galactic plane by 7/sup 0/ and inclined to the line of sight by 72/sup 0/, but the sheet of high-density gas which surrounds Sgr A and B is not measurably tilted. Spectra of the /sup 12/CO and C/sup 18/O emission lines near lambda = 2.60 and 2.73 mm were taken along eight lines of sight within the survey region to estimate the excitation temperatures and column densities: two 16' x 16' densely sampled maps were made in /sup 13/CO to estimate cloud sizes. Isocyanic acid (HNCO) was fortuitously found at four of these positions in emission with large velocity widths. Two forms of molecular gas were seen in the central region: (1) clouds with radii of 20 pc, excitation temperatures approximately 8 K, and mass of approximately 10/sup 5/ mass of sun and (2) diffuse regions with T/sub x/ of 25K, densities of > 5 x 10/sup 4/ cm/sup -3/, and linewidths > 30 km s/sup -1/. A total mass of roughly 1.2 x 10/sup 8/ Mass of sun was derived for the interstellar matter in the inner 400 pc of the Galaxy. A model of closed orbits in a barlike bulge potential was developed to simulate the kinematic motions of the gas in the inner 400 pc of the Galaxy. The modelaccounts for most but not all of the high-velocity features, the + 135 km s/sup -1/ expanding arm being the most difficult to explain.
- Research Organization:
- Princeton Univ., NJ (USA)
- OSTI ID:
- 6913800
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
MILKY WAY
COSMIC GASES
CARBON MONOXIDE
EMISSION SPECTRA
INTERSTELLAR SPACE
ISOCYANIC ACID
MASS
MATHEMATICAL MODELS
MICROWAVE RADIATION
MOLECULES
SIZE
ULTRALOW TEMPERATURE
CARBON COMPOUNDS
CARBON OXIDES
CARBONIC ACID DERIVATIVES
CHALCOGENIDES
ELECTROMAGNETIC RADIATION
FLUIDS
GALAXIES
GASES
NITROGEN COMPOUNDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
SPACE
SPECTRA
640105* - Astrophysics & Cosmology- Galaxies