J/A+A/641/A53 Giant molecular filament GMF54 images (Wang+, 2020)
Dense gas in a giant molecular filament.
Wang Y., Beuther H., Schneider N., Meidt S.E., Linz H., Ragan S.,
Zucker C., Battersby C., Soler J.D., Schinnerer E., Bigiel F., Colombo D.,
Henning T.
<Astron. Astrophys. 641, A53 (2020)>
=2020A&A...641A..53W 2020A&A...641A..53W (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Molecular clouds ; Radio lines
Keywords: ISM: clouds - ISM: molecules - stars: formation - radio lines: ISM
Abstract:
Recent surveys of the Galactic plane in the dust continuum and CO
emission lines reveal that large (≳50pc) and massive
(≳105M☉) filaments, know as giant molecular filaments (GMFs),
may be linked to galactic dynamics and trace the mid-plane of the
gravitational potential in the Milky Way. Yet our physical
understanding of GMFs is still poor.
We investigate the dense gas properties of one GMF, with the ultimate
goal of connecting these dense gas tracers with star formation
processes in the GMF.
We have imaged one entire GMF located at l∼52-54° longitude, GMF54
(∼68pc long), in the empirical dense gas tracers using the HCN(1-0),
HNC(1-0), HCO+(1-0) lines, and their 13C isotopologue transitions,
as well as the N2H+1-0) line. We study the dense gas distribution,
the column density probability density functions (N-PDFs) and the line
ratios within the GMF.
The dense gas molecular transitions follow the extended structure of
the filament with area filling factors between 0.06 and 0.28 with
respect to 13CO(1-0). We constructed the N-PDFs of H2 for each of
the dense gas tracers based on their column densities and assumed
uniform abundance. The N-PDFs of the dense gas tracers appear curved
in log-log representation, and the HCO+ NPDF has the largest
log-normal width and flattest power-law slope index. Studying the
N-PDFs for sub-regions of GMF54, we found an evolutionary trend in the
N-PDFs that high-mass star forming and Photon Dominated Regions (PDRs)
have flatter power-law indices. The integrated intensity ratios of the
molecular lines in GMF54 are comparable to those in nearby galaxies.
In particular, the N2H+/13CO ratio, which traces the dense gas
fraction, has similar values in GMF54 and all nearby galaxies except
Ultraluminous Infrared Galaxies (ULIRGs).
As the largest coherent cold gaseous structure in our Milky Way, GMFs,
are outstanding candidates for connecting studies of star formation on
Galactic and extragalactic scales. By analyzing a complete map of the
dense gas in a GMF we have found that: (1) the dense gas N-PDFs appear
flatter in more evolved regions and steeper in younger regions, and
(2) its integrated dense gas intensity ratios are similar to those of
nearby galaxies.
Description:
The giant filament GMF54 was observed with the IRAM 30m
telescope in September 2017 and November 2017 with the EMIR receiver
and the Fourier Transform Spectrometer (FTS) backends at 3mm.
FITS files produced and used in the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 172 31 List of fits images and datacubes
fits/* . 31 Individual fits images and datacubes
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See also:
J/A+A/634/A139 : Giant Molecular Filament THOR datacubes (Wang+, 2020)
J/A+A/638/A44 : Infrared dark cloud G28.3 HI and CI maps (Beuther+, 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 of center (J2000)
11- 19 F9.5 deg GLAT Galactic latitude center (J2000)
21- 23 I3 --- Nx Number of pixels along X-axis
25- 27 I3 --- Ny Number of pixels along Y-axis
29- 31 I3 --- Nz ? Number of slices for the datacubes
33- 38 I6 m/s bVRAD ? Lower value of VRAD velocity
for the datacubes
40- 44 I5 m/s BVRAD ? Upper value of VRAD velocity
for the datacubes
46- 48 I3 m/s dVRAD ? VRAD resolution for the datacubes
50- 54 I5 Kibyte size Size of FITS file
56-107 A52 --- FileName Name of FITS file, in subdirectory fits
109-172 A64 --- Title Title of the FITS file
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Acknowledgements:
Yuan Wang, wang(at)mpia.de
(End) Patricia Vannier [CDS] 29-Jun-2020