J/A+A/657/A1 Maggie filament datacubes (Syed+, 2022)
The "Maggie" filament: Physical properties of a giant atomic cloud.
Syed J., Soler J.D., Beuther H., Wang Y., Suri S., Henshaw J.D., Riener M.,
Bialy S., Rezaei Kh.S., Stil J.M., Goldsmith P.F., Rugel M.R.,
Glover S.C.O., Klessen R.S., Kerp J., Urquhart J.S., Ott J., Roy N.,
Schneider N., Smith R.J., Longmore S.N., Linz H.
<Astron. Astrophys. 657, A1 (2022)>
=2022A&A...657A...1S 2022A&A...657A...1S (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Molecular clouds ; Radio lines
Keywords: ISM: clouds - ISM: atoms - ISM: kinematics and dynamics -
ISM: structure - radio lines: ISM
Abstract:
The atomic phase of the interstellar medium plays a key role in the
formation process of molecular clouds. Due to the line-of-sight
confusion in the Galactic plane that is associated with its ubiquity,
atomic hydrogen emission has been challenging to study.
We investigate the physical properties of the "Maggie" filament, a
large-scale filament identified in HI emission at line-of-sight
velocities, vLSR~-54km/s.
Employing the high-angular resolution data from The HI/OH
Recombination line survey of the inner Milky Way (THOR), we have been
able to study HI emission features at negative vLSR velocities
without any line-of-sight confusion due to the kinematic distance
ambiguity in the first Galactic quadrant. In order to investigate the
kinematic structure, we decomposed the emission spectra using the
automated Gaussian fitting algorithm GaussPy+.
We identify one of the largest, coherent, mostly atomic HI filaments
in the Milky Way. The giant atomic filament Maggie, with a total
length of 1.2±0.1kpc, is not detected in most other tracers, and it
does not show signs of active star formation. At a kinematic distance
of 17kpc, Maggie is situated below (by ∼500pc), but parallel to, the
Galactic HI disk and is trailing the predicted location of the Outer
Arm by 5-10km/s in longitude-velocity space. The centroid velocity
exhibits a smooth gradient of less than 3(km/s)/(10pc) and a coherent
structure to within ±6km/s. The line widths of ∼10km/s along the
spine of the filament are dominated by nonthermal effects. After
correcting for optical depth effects, the mass of Maggie's dense spine
is estimated to be 7.2x105 solar masses. The mean number density of
the filament is ∼4cm-3, which is best explained by the filament
being a mix of cold and warm neutral gas. In contrast to molecular
filaments, the turbulent Mach number and velocity structure function
suggest that Maggie is driven by transonic to moderately supersonic
velocities that are likely associated with the Galactic potential
rather than being subject to the effects of self-gravity or stellar
feedback. The probability density function of the column density
displays a log-normal shape around a mean of 4.8x1020cm-2, thus
reflecting the absence of dominating effects of gravitational
contraction.
Description:
While Maggie's origin remains unclear, we hypothesize that Maggie
could be the first in a class of atomic clouds that are the precursors
of giant molecular filaments.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 117 3 List of fits datacubes
fits/* . 3 Individual fits datacubes
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See also:
J/A+A/580/A112 : THOR. The HI, OH, Recombination Line Survey (Bihr+, 2015)
J/A+A/634/A83 : THOR DR2 source list (Wang+, 2020)
J/A+A/634/A139 : Giant Molecular Filament THOR datacubes (Wang+, 2020)
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 Galactic 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
33- 37 I5 Kibyte size Size of FITS file
39- 75 A37 --- FileName Name of FITS file, in subdirectory fits
77-117 A41 --- Title Title of the FITS file
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Acknowledgements:
Jonas Syed, syed(at)mpia-hd.mpg.de
(End) Patricia Vannier [CDS] 09-Nov-2021