J/A+A/634/A139 Giant Molecular Filament THOR datacubes (Wang+, 2020)
Cloud formation in the atomic and molecular phase:
HI self absorption (HISA) towards a giant molecular filament.
Wang Y., Bihr S., Beuther H., Rugel M.R., Soler J.D., Ott J.,
Kainulainen J., Schneider N., Klessen R.S., Glover S.C.O.,
McClure-Griffiths N.M., Goldsmith P.F., Johnston K.G., Menten K.M.,
Ragan S., Anderson L.D., Urquhart J.S., Linz H., Roy N., Smith R.J.,
Bigiel F., Henning T., Longmore S.N.
<Astron. Astrophys. 634, A139 (2020)>
=2020A&A...634A.139W 2020A&A...634A.139W (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Molecular clouds ; Radio lines
Keywords: ISM: atoms - ISM: clouds - ISM: molecules - radio lines: ISM -
stars: formation
Abstract:
Molecular clouds form from the atomic phase of the interstellar
medium. However, characterizing the transition between the atomic and
the molecular interstellar medium (ISM) is a complex observational
task. Here we address cloud formation processes by combining HI self
absorption (HISA) with molecular line data. Column density probability
density functions (N-PDFs) are a common tool for examining molecular
clouds. One scenario proposed by numerical simulations is that the
N-PDF evolves from a log-normal shape at early times to a
power-law-like shape at later times. To date, investigations of N-PDFs
have been mostly limited to the molecular component of the cloud. In
this paper, we study the cold atomic component of the giant molecular
filament GMF38.1-32.4a (GMF38a, distance=3.4kpc, length∼230pc),
calculate its N-PDFs, and study its kinematics. We identify an
extended HISA feature, which is partly correlated with the 13CO
emission. The peak velocities of the HISA and 13CO observations agree
well on the eastern side of the filament, whereas a velocity offset of
approximately 4km/s is found on the western side. The sonic Mach
number we derive from the linewidth measurements shows that a large
fraction of the HISA, which is ascribed to the cold neutral medium
(CNM), is at subsonic and transonic velocities. The column density of
the CNM part is on the order of 1020 to 1021cm-2. The column
density of molecular hydrogen, traced by 13CO, is an order of
magnitude higher. The N-PDFs from HISA (CNM), HI emission (the warm
and cold neutral medium), and 13CO (molecular component) are well
described by log-normal functions, which is in agreement with
turbulent motions being the main driver of cloud dynamics. The N-PDF
of the molecular component also shows a power law in the high
column-density region, indicating self-gravity. We suggest that we are
witnessing two different evolutionary stages within the filament. The
eastern subregion seems to be forming a molecular cloud out of the
atomic gas, whereas the western subregion already shows high column
density peaks, active star formation, and evidence of related feedback
processes.
Description:
hisaspectrumTHORandVGPS-pol-4.fits and
hisaspectrumTHORandVGPS-pol-2.fits are the HISA spectra datacube
we extracted with fourth and second order polynomial function fitting
method.
hisaspectrumTHORandVGPS-pol-2fitvelo.fits,
hisaspectrumTHORandVGPS-pol-2fitFWHM.fits,
hisaspectrumTHORandVGPS-pol-2fitamp.fits are the peak velocity,
full width half maximum line width and peak intensity images derived
from Gaussian fitting of the HISA spectra extracted with second order
polynomial to estimate the background emission.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 262 5 List of fits files
fits/* . 5 Individual fits files
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [G]
2- 10 F9.5 deg GLON Galactic longitude
11- 19 F9.5 deg GLAT Galaxtic latitude
21- 24 I4 --- Nx Number of pixels along X-axis
26- 28 I3 --- Ny Number of pixels along Y-axis
30- 31 I2 --- Nz ? Number of slices for the datacubes
33- 34 I2 km/s bVRAD ? Lower value of VRAD interval for the datacubes
36- 37 I2 km/s BVRAD ? Upper value of VRAD interval for the datacubes
39- 41 F3.1 km/s dVRAD ? VRAD resolution for the datacubes
43- 48 I6 Kibyte size Size of FITS file
50- 96 A47 --- FileName Name of FITS file, in subdirectory fits
98-262 A165 --- Title Title of the FITS file
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Acknowledgements:
Yuan Wang, wang(at)mpia.de
(End) Patricia Vannier [CDS] 15-Jan-2020