A fragmentary cold H I cloud near W3 and W4

Journal Article · Sun May 01 04:00:00 EDT 1983 · Astron. J.; (United States)

DOI:https://doi.org/10.1086/113355· OSTI ID:6052101

Hasegawa, T; Sato, F; Fukui, Y

A cold H I cloud appears as self-absorption dips in the 21-cm line profiles in and around the giant molecular cloud near W3 and W4. The cloud extends nearly along the galactic plane from the western edge of W4 to approx.150 pc west. The cold H I cloud consists of several fragments typically approx.25 pc in diameter. Their distribution coincides in part with that of the CO cloud, while the fragments are found well beyond the limit of the CO detection. The total particle density in the fragments is estimated to be 20--35 cm/sup -3/, which corresponds to the (H/sub 2/)/(H I) ratio of 15--50. Each fragment shows no sign of systematic motions such as rotation or collapse. The mass of a fragment inferred from the virial theorem is (1--4) x 10/sup 4/ M/sub sun/ and the total mass of the H I cloud summed up for all the fragments amounts to > or approx. =1.7 x 10/sup 5/ M/sub sun/. This indicates that the mass of the W3/W4 molecular-cloud complex is larger by a factor of approx.2 than that estimated by CO observations. At the layer of enhanced CO brightness adjoining the H II region, the H I dip disappears suddenly suggesting that the (H/sub 2/)/(H I) ratio is larger there.

• Research Organization: Department of Astronomy, University of Tokyo, Bunkyo-ku, Tokyo 113, Japan
• OSTI ID: 6052101
• Journal Information: Astron. J.; (United States), Journal Name: Astron. J.; (United States) Vol. 88:5; ISSN ANJOA
• Country of Publication: United States
• Language: English

Related Subjects

640103* -- Astrophysics & Cosmology-- Quasi-Stellar
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640105 -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
COSMIC RADIO SOURCES
DISTRIBUTION
ELECTROMAGNETIC RADIATION
FREQUENCY RANGE
GALAXIES
GHZ RANGE
GHZ RANGE 01-100
H1 REGIONS
MILKY WAY
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
RADIOWAVE RADIATION
SPATIAL DISTRIBUTION