J/PASJ/72/43 FUGIN. VII. Galactic plane HI clouds (Nakanishi+, 2020)
FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope
(FUGIN). VII. Molecular fraction of HI clouds.
Nakanishi H., Fujita S., Tachihara K., et AL.
<Publ. Astron. Soc. Jap., 72, 43 (2020)>
=2020PASJ...72...43N 2020PASJ...72...43N (SIMBAD/NED BibCode)
ADC_Keywords: Galactic plane ; Molecular clouds ; H I data ; Velocity dispersion
Abstract:
We analyze molecular-gas formation in neutral atomic hydrogen (HI)
clouds using the latest CO data, obtained from the FOREST (four-beam
receiver system on the 45m telescope) unbiased Galactic plane imaging
survey with the Nobeyama 45m telescope, and using HI data taken from
the Very Large Array Galactic plane survey. We applied a dendrogram
algorithm to the HI data cube to identify HI clouds, and we calculated
the HI mass and molecular-gas mass by summing the CO line intensity
within each HI cloud. On the basis of the results, we created a
catalog of 5737 identified HI clouds with local standard of rest (LSR)
velocity of VLSR≤-20km/s in galactic longitude and latitude ranges of
20°≤l≤50° and -1°≤b≤1°, respectively. We found
that most of the HI clouds are distributed within a Galactocentric
distance of 16kpc, and most of them are in the cold neutral medium
phase. In addition, we determined that the high-mass end of the HI
mass function is fitted well with a power-law function with an index
of 2.3. Although two sequences of self-gravitating and diffuse clouds
are expected to appear in the Mtot-MH2 diagram according to
previous works based on a plane-parallel model, the observational data
show only a single sequence with large scattering within these two
sequences. This implies that most of the clouds are mixtures of these
two types of clouds. Moreover, we suggest the following scenario of
molecular-gas formation: an HI-dominant cloud evolved with increasing
H2 mass along a path of MH2∝M2tot by collecting diffuse
gas before reaching and moving along the curves of the two sequences.
Description:
We applied the dendrogram analysis to the VGPS HI data cube to create
a catalog of HI clouds of the outer Galaxy, including the masses of
H2 gas within each HI cloud, which were estimated by using FUGIN CO
survey data.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 92 5737 Identified HI clouds
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See also:
J/AJ/122/3155 : Peculiar HI cloud near galactic plane (Higgs+, 2001)
J/ApJ/626/887 : HI clouds in Southern Galactic Plane Survey (Kavars+, 2005)
J/ApJ/722/367 : HI clouds in Quadrant I of the Milky Way (Ford+, 2010)
J/ApJ/770/L4 : HI clouds around the Galactic Center (McClure-Griffiths+, 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID [1/5737] Sequential number
8- 12 F5.2 deg GLON Galactic longitude
16- 20 F5.2 deg GLAT Galactic longitude
22- 26 F5.1 km/s VLSR LSR velocity
29- 32 F4.1 kpc D Heliocentric distance
35- 38 F4.1 kpc R Galactocentric distance
40- 43 F4.1 pc Rmin Minor-axis radius
45- 48 F4.1 pc Rmaj Major-axis radius
50- 55 F6.1 deg PA [] Position angle
58- 60 F3.1 km/s sigma Velocity dispersion
63- 69 F7.1 Msun MHI HI mass
74- 76 F3.1 Msun e_MHI rms uncertainty on MHI
79- 85 F7.1 Msun MH2 H2 mass
90- 92 F3.1 Msun e_MH2 rms uncertainty on MH2
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History:
From electronic version of the journal
References:
Umemoto et al., Paper I 2017PASJ...69...78U 2017PASJ...69...78U
Kohno et al., Paper II 2018PASJ...70S..50K 2018PASJ...70S..50K
Nishimura et al., Paper III 2018PASJ...70S..42N 2018PASJ...70S..42N
Sofue et al., Paper IV 2019PASJ...71S...1S 2019PASJ...71S...1S
Torii et al., Paper V 2019PASJ...71S...2T 2019PASJ...71S...2T
Kohno et al., Paper VI 2021PASJ...73S.129K 2021PASJ...73S.129K
Nishimura et al., Paper VIII 2021PASJ...73S.285N 2021PASJ...73S.285N
(End) Patricia Vannier [CDS] 22-Apr-2021