J/A+A/633/A14 GaussPy+ decomposition of Galactic Ring Survey (Riener+, 2020)
Autonomous Gaussian decomposition of the Galactic Ring Survey.
I. Global statistics and properties of the 13CO emission data.
Riener M., Kainulainen J., Beuther H., Henshaw J.D., Orkisz J.H., Wang Y.
<Astron. Astrophys. 633, A14 (2020)>
=2020A&A...633A..14R 2020A&A...633A..14R (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Galactic plane ; Spectra, millimetric/submm ;
Radio lines ; Interstellar medium ; Velocity dispersion
Keywords: methods: data analysis - radio lines: general -
ISM: kinematics and dynamics - ISM: lines and bands
Abstract:
The analysis of large molecular line surveys of the Galactic plane is
essential for our understanding of the gas kinematics on Galactic
scales and, in particular, its link with the formation and evolution
of dense structures in the interstellar medium. An approximation of
the emission peaks with Gaussian functions allows for an efficient and
straightforward extraction of useful physical information contained in
the shape and Doppler-shifted frequency of the emission lines
contained in these enormous data sets. In this work, we present an
overview and the first results of a Gaussian decomposition of the
entire Galactic Ring Survey (GRS) 13CO (1-0) data that consists of
about 2.3 million spectra. We performed the decomposition with the
fully automated GaussPy+ algorithm and fitted about 4.6 million
Gaussian components to the GRS spectra. These decomposition results
enable novel and unexplored ways to interpret and study the gas
velocity structure. We discuss the statistics of the fit components
and relations between the fitted intensities, velocity centroids, and
velocity dispersions. We find that the magnitude of the velocity
dispersion values increase towards the inner Galaxy and around the
Galactic midplane, which we speculate is partly due to the influence
of the Galactic bar and regions with higher non-thermal motions
located in the midplane, respectively. We also used our decomposition
results to infer global properties of the gas emission and find that
the number of fit components used per spectrum is indicative of the
amount of structure along the line of sight. We find that the emission
lines from regions located on the far side of the Galaxy show
increased velocity dispersion values, which are likely due to beam
averaging effects. We demonstrate how this trend has the potential to
aid in characterising Galactic structure by disentangling emission
that belongs to the nearby Aquila Rift molecular cloud from emission
that is more likely associated with the Perseus and Outer spiral arms.
With this work, we also make our entire decomposition results
available.
Description:
The catalogue contains the Gaussian decomposition results obtained
with GaussPy+ (Riener et al., 2019A&A...628A..78R 2019A&A...628A..78R) for the entire
Galactic Ring Survey GRS data set
(https://www.bu.edu/galacticring/new_data.html) at its full spatial
and spectral resolution. In total, ∼4.6 million Gaussian components
were fitted to the ∼2.3 million 13CO emission line spectra of the
GRS. Especially spectra from lines of sight near the Galactic midplane
showed great complexity, requiring 10 or more fit components for a
good decomposition.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 107 5134488 Decomposition results
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See also:
https://www.bu.edu/galacticring/new_data.html : GRS survey Home Page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 pix Xpos [0/6829] Pixel position in Galactic longitude
6- 8 I3 pix Ypos [0/357] Pixel position in Galactic latitude
10- 15 F6.3 deg GLON [14.002/56.0] Galactic longitude position
17- 22 F6.3 deg GLAT [-1.1/1.096] Galactic latitude position
24- 28 F5.2 K TB [0.08/25.57] Fitted peak main beam brightness
temperature value
30- 34 F5.2 K e_TB [0.0/14.62]? Uncertainty in TB (1)
36- 41 F6.2 km/s VLSR [-4.95/134.89] Fitted centroid velocity value
43- 48 F6.2 km/s e_VLSR [0.0/10.0]? Uncertainty in VLSR (1)
50- 57 F8.2 km/s sigma [0.09/49.12] Fitted velocity dispersion value
59- 63 F5.2 km/s e_sigma [0.0/15.93]? Uncertainty in sigma (1)
65- 68 F4.2 K rms [0.04/1.56] Root-mean-square noise value of
spectrum
70- 75 F6.1 % pvalue [0.0/99.0] p-value of normality test for
normally distributed residual values
77- 83 F7.1 --- aicc Value of corrected Akaike information criterion
85- 91 F7.2 --- rchi2 Value of reduced chi-squared
93- 94 I2 --- Ncomp [1/23] Number of Gaussian fit components
96- 97 I2 --- Nmed [0/15] Weighted median number of fit components
determined from neighbouring fit solutions
99 I1 --- Njump [0/8] Number of component jumps (>2) towards
directly neighbouring fit solutions
101 I1 --- F1 [0/1] Strongly blended with another fit
component
103 I1 --- F2 [0/1] Negative residual feature introduced
by fit component
105 I1 --- F3 [0/1] Comparatively broad fit component
107 I1 --- F4 [0/7] Centroid velocity of fit component not
compatible with neighboring fit solutions
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Note (1): Estimated uncertainty values for the fit components were replaced with
NULL values in case one of the following criteria was fulfilled:
e_TB>TB, e_VLSR>10.0km/s, e_sigma>sigma.
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Acknowledgements:
Manuel Riener, riener(at)mpia.de
(End) Manuel Riener [MPIA, Germany], Patricia Vannier [CDS] 20-Nov-2019