2014/01/31 by Yasuo Fukui, Ryuji Okamoto, Ryohei Kaji +10 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Cloud computing #Conjunction (astronomy) #Envelope (radar) #Galaxies: Formation, Evolution, Phenomena #High latitude #Latitude #Optical depth #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/796/1/59
published as The Astrophysical Journal, Volume 796, Issue 1, article id. 59, 11 pp. (2014)
openalex publication_date 2014/11/05 · arxiv created 2014/11/21 · arxiv updated 2014/11/24 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present an analysis of the and CO gas in conjunction with the Planck / IRAS submillimeter/far-infrared dust properties toward the most outstanding high latitude clouds MBM 53, 54, 55 and HLCG 92 − 35 at b = −30° to − 45°. The CO emission, dust opacity at 353 GHz (τ 353 ), and dust temperature ( T d ) show generally good spatial correspondence. On the other hand, the correspondence between the emission and the dust properties is less clear than in CO. The integrated intensity and τ 353 show a large scatter with a correlation coefficient of ∼0.6 for a T d range from 16 K to 22 K. We find, however, that and τ 353 show better correlation for smaller ranges of T d every 0.5 K, generally with a correlation coefficient of 0.7–0.9. We set up a hypothesis that the gas associated with the highest T d ⩾ 21.5 K is optically thin, whereas the emission is generally optically thick for T d lower than 21.5 K. We have determined a relationship for the optically thin gas between atomic hydrogen column density and τ 353 , , under the assumption that the dust properties are uniform and we have applied this to estimate from τ 353 for the whole cloud. was then used to solve for T s and over the region. The result shows that the is dominated by optically thick gas having a low spin temperature of 20–40 K and a density of 40–160 cm −3 . The envelope has a total mass of ∼1.2 × 10 4 M ☉ , an order of magnitude larger than that of the CO clouds. The envelope properties derived by this method do not rule out a mixture of and H 2 in the dark gas, but we present indirect evidence that most of the gas mass is in the atomic state.