Molecular and atomic clouds associated with infrared cirrus in Ursa Major

Journal Article · Sat Aug 01 04:00:00 EDT 1987 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/165492· OSTI ID:5710911

De Vries, H W; Thaddeus, P; Heithausen, A

Observations of CO and H I revealed that in Ursa Major the high-latitude far-infrared cirrus emission discovered by the Infrared Astronomical Satellite comes from molecular and atomic clouds. These clouds differ sufficiently from the large clouds in the Galactic plane so that the ratio of H/sub 2/ column density to velocity-integrated CO radiation temperature, N(H/sub 2/)/W(CO), derived from Galactic plane surveys, may not apply to them. On the assumption of a constant gas-to-dust ratio, it is argued that the cirrus emission in Ursa Major is a good mass tracer, since both the atomic and the molecular gas are probably optically thin at visual wavelengths, and the grains are heated not by local sources but by the background field of Galactic starlight. The N(H/sub 2/)/W(CO) ratio thus derived for those diffuse clouds, is significantly lower than the ratio applicable to Galactic plane surveys. 29 references.

• Research Organization: Columbia Univ., NY; Bonn Universitaet, West Germany
• OSTI ID: 5710911
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 319; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATOMS
BINARY STARS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
COSMIC DUST
COSMIC GASES
DUSTS
ELEMENTS
FLUIDS
GALAXIES
GASES
HYDROGEN
INFRARED SPECTRA
INTERSTELLAR SPACE
MILKY WAY
MOLECULES
NEBULAE
NONMETALS
OXIDES
OXYGEN COMPOUNDS
SPACE
SPECTRA
STARS