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

• Published in: The Astrophysical journal Vol. 796; no. 1; pp. 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: Journal Article
• Language: English
• Published: United States 20.11.2014
• 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
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/796/1/59

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).