H I, CO, AND PLANCK/IRAS DUST PROPERTIES IN THE HIGH LATITUDE CLOUD COMPLEX, MBM 53, 54, 55 AND HLCG 92-35. POSSIBLE EVIDENCE FOR AN OPTICALLY THICK H I ENVELOPE AROUND THE CO CLOUDS

We present an analysis of the HI and CO gas in conjunction with the Planck/IRAS submillimeter/far-infrared dust properties toward the most outstanding high latitude clouds MBM53, 54, 55 and HLCG92-35 at b = -30[degrees] to -45[degrees]. We set up a hypothesis that the HI gas associated with the high...

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Bibliographic Details
Published in:The Astrophysical journal 2014-11, Vol.796 (1), p.1-11
Main Authors: Fukui, Yasuo, Okamoto, Ryuji, Kaji, Ryohei, Yamamoto, Hiroaki, Torii, Kazufumi, Hayakawa, Takahiro, Tachihara, Kengo, Dickey, John M, Okuda, Takeshi, Ohama, Akio, Kuroda, Yutaka, Kuwahara, Toshihisa
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
CARBON MONOXIDE
Clouds
CORRELATIONS
COSMIC GASES
DENSITY
Dust
DUSTS
EMISSION
Estimates
GHZ RANGE
HYDROGEN
HYPOTHESIS
Latitude
MASS
OPACITY
SPIN
Spin temperature
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Summary:We present an analysis of the HI and CO gas in conjunction with the Planck/IRAS submillimeter/far-infrared dust properties toward the most outstanding high latitude clouds MBM53, 54, 55 and HLCG92-35 at b = -30[degrees] to -45[degrees]. We set up a hypothesis that the HI gas associated with the highest T sub(d) [> or =, slanted] 21.5K is optically thin, whereas the HIi emission is generally optically thick for T sub(d) lower than 21.5K. We have determined a relationship for the optically thin HI gas between atomic hydrogen column density and [tau] sub(353), N sub(H I) (cm super(-2)) = (1.5 x 10 super(26)) [middot] [tau] sub(353), under the assumption that the dust properties are uniform and we have applied this to estimate NHi from [tau] sub(353) for the whole cloud. The result shows that the HI is dominated by optically thick gas having a low spin temperature of 20-40K and a density of 40-160 cm super(-3).
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/796/1/59