J/A+A/638/A44 Infrared dark cloud G28.3 HI and CI maps (Beuther+, 2020)
Dynamical cloud formation traced by atomic and molecular gas.
Beuther H., Wang Y., Soler J.D., Linz H., Henshaw J., Vazquez-Semadeni E.,
Gomez G., Ragan S., Henning T., Glover S.C.O., Lee M.-Y., Guesten R.
<Astron. Astrophys. 638, A44 (2020)>
=2020A&A...638A..44B 2020A&A...638A..44B (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Infrared sources
Keywords: ISM: clouds - ISM: kinematics and dynamic - ISM: structure -
ISM: general - evolution - stars: formation
Abstract:
Atomic and molecular cloud formation is a dynamical process. However,
kinematic signatures of these processes are still observationally
poorly constrained.
Identify and characterize the cloud formation signatures in atomic and
molecular gas.
Targeting the cloud-scale environment of the prototypical infrared
dark cloud G28.3, we employ spectral line imaging observations of the
two atomic lines HI and [CI] as well as molecular lines observations
in 13CO in the 1-0 and 3-2 transitions. The analysis comprises
investigations of the kinematic properties of the different tracers,
estimates of the mass flow rates, velocity structure functions, a
Histogram of Oriented Gradients (HOG) study as well as comparisons to
simulations.
The central IRDC is embedded in a more diffuse envelope of cold neutral
medium (CNM) traced by HI self-absorption (HISA) and molecular gas.
The spectral line data as well as the HOG and structure function
analysis indicate a possible kinematic decoupling of the HI from the
other gas compounds. Spectral analysis and position-velocity diagrams
reveal two velocity components that converge at the position of the
IRDC. Estimated mass flow rates appear rather constant from the cloud
edge toward the center. The velocity structure function analysis is
consistent with gas flows being dominated by the formation of
hierarchical structures.
The observations and analysis are consistent with a picture where the
IRDC G28 is formed at the center of two converging gas flows. While
the approximately constant mass flow rates are consistent with a
self-similar, gravitationally driven collapse of the cloud, external
compression by, e.g., spiral arm shocks or supernovae explosions
cannot be excluded yet. Future investigations should aim at
differentiating the origin of such converging gas flows.
Description:
The HI data are taken from the HI/OH/Recombination lines survey of the
Milky Way (THOR, Beuther et al. 2016A&A...595A..32B 2016A&A...595A..32B; Wang et al. 2019,
2020A&A...634A..83W 2020A&A...634A..83W, Cat. J/A+A/634/A83) conducted with the Very Large
Array (VLA).
The atomic carbon [CI] and 13CO(3-2) data were observed with the
APEX telescope1 in several observing runs between May and July 2018
(project ID M9504A 101).
Objects:
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RA (2000) DE Designation(s)
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18 42 52.61 -04 00 12.5 G28.3 = MSX6C G028.3937+00.0757
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 159 3 List of fits files
fits/* . 3 Indivifual fits files
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See also:
J/A+A/634/A83 : THOR DR2 source list (Wang+, 2020)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 30 I3 --- Nz Number of pixels along Z-axis
32- 52 A21 "datime" Obs.date Observaiton date
54- 55 I2 km/s bVRAD Lower value of VRAD interval
57- 61 F5.1 km/s BVRAD Upper value of VRAD interval
63- 66 I4 m/s dVRAD VRAD resolution
68- 71 I4 Kibyte size Size of FITS file
73- 93 A21 --- FileName Name of FITS file, in subdirectory fits
95-159 A65 --- Title Title of the FITS file
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Acknowledgements:
Henrik Beuther, beuther(at)mpia.de
(End) Patricia Vannier [CDS] 20-Apr-2020