J/A+A/658/A54 Molecular cloud assoc. to Milky Way spiral arms (Colombo+, 2022)
The SEDIGISM survey: The influence of spiral arms on the molecular gas
distribution of the inner Milky Way.
Colombo D., Duarte-Cabral A., Pettitt A.R., Urquhart J.S., Wyrowski F.,
Csengeri T., Neralwar K.R., Schuller F., Menten K.M., Anderson L.,
Barnes P., Beuther H., Bronfman L., Eden D., Ginsburg A., Henning T.,
Koenig C., Lee M.-Y., Mattern M., Medina S., Ragan S.E., Rigby A.J.,
Sanchez-Monge A., Traficante A., Yang A.Y., Wienen M.
<Astron. Astrophys. 658, A54 (2022)>
=2022A&A...658A..54C 2022A&A...658A..54C (SIMBAD/NED BibCode)
ADC_Keywords: Galactic plane; Interstellar medium; Molecular clouds
Keywords: ISM: clouds - Galaxy: structure - stars: formation - galaxies: ISM -
galaxies: star formation - galaxies: spiral
Abstract:
The morphology of the Milky Way is still a matter of debate. In order
to shed light on the uncertainty surrounding the Galactic structure,
in this paper, we study the imprint of spiral arms on the molecular
gas distribution and properties. To do so, we take full advantage of
the SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic
Interstellar Medium) survey that observed a large area of the inner
Galaxy in the 13CO(2-1) line at an angular resolution of 28". We
analyse the influences of spiral arms by considering the features of
the molecular gas emission as a whole across the longitude- velocity
map built from the full survey. Additionally, we examine the
properties of the molecular clouds in the spiral arms compared to
those in the inter-arm regions. Through flux and luminosity
probability distribution functions, we find that the molecular gas
emission associated with the spiral arms does not differ much from the
emission between the arms. On average, spiral arms show masses per
unit length of ∼105-106M☉/kpc. This is similar to values
inferred from data sets in which emission distributions were segmented
into molecular clouds. By examining the cloud distribution across the
Galactic plane, we infer that the molecular mass in the spiral arms is
a factor of 1.5 higher than that of the inter-arm medium, similar to
what is found for other spiral galaxies in the local Universe. We
observe that only the distributions of cloud mass surface densities
and aspect ratio in the spiral arms show significant differences
compared to those of the inter-arm medium; other observed differences
appear instead to be driven by a distance bias. By comparing our
results with simulations and observations of nearby galaxies, we
conclude that the measured quantities would classify the Milky Way as
a flocculent spiral galaxy, rather than as a grand-design one.
Description:
In this work we study how the Milky Way spiral arms impact the
molecular gas properties in the inner Galaxy using SEDIGISM
13CO(2-1) data (Schuller et al., 2021MNRAS.500.3064S 2021MNRAS.500.3064S). SEDIGISM data
has been taken using the APEX telescope. The SEDIGISM survey mapped
84deg2 of the Galactic plane between -60<l<31° in several
molecular transitions (including 13CO(2-1)) and presents an angular
resolution of 30 arcsec and a velocity resolution of 0.25km/s. The
complete molecular cloud catalogue from SEDIGISM data is obtained by
Duarte-Cabral et al. (2021MNRAS.500.3027D 2021MNRAS.500.3027D). Table 1 includes the
results of the association of each molecular cloud to a given spiral
arm structure or an inter-arm region through Taylor & Cordes
(1993ApJ...411..674T 1993ApJ...411..674T).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 51 10663 Molecular cloud association to spiral arms
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Seq [1/10663] Unique cloud ID number
7- 23 A17 --- Name Cloud name as per the SEDIGISM naming scheme,
i.e. SDG followed by the Galactic coordinates
of the cloud (SDGLLL.lll+B.bbb)
25- 31 A7 --- SpiralArm Name of the closest spiral arm (1)
33- 36 F4.2 kpc DistMin Distance to the closest spiral arm calculated
on the Galactocentric xy plane
38- 43 F6.2 km/s DeltaV Velocity offset with respect to the
closest spiral arm
45- 48 F4.2 --- Pvalue p-value from the chi2 test that associates
cloud position to the spiral arm model on
the Galactocentric xy plane
50- 51 A2 --- Location Location of the molecular cloud:
spiral arms (SA) or inter-arm region (IA)
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Note (1): Name of the closest spiral arm as follows:
3kpc = 3 kpc arms
Sag-Car = Sagittarius-Carina arm
Scu-Cen = Scutum-Centaurus arm
Perseus = Perseus arm
Nor-Out = Norma-Outer arm
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Acknowledgements:
Dario Colombo, dcolombo(at)mpifr-bonn.mpg.de
(End) Patricia Vannier [CDS] 01-Oct-2021