J/A+A/645/A113 Southern outer Galaxy star forming regions (Koenig+, 2021)
A new search for star forming regions in the southern outer Galaxy.
Koenig C., Urquhart J.S., Wyrowski F., Colombo D., Menten K.M.
<Astron. Astrophys. 645, A113 (2021)>
=2021A&A...645A.113K 2021A&A...645A.113K (SIMBAD/NED BibCode)
ADC_Keywords: Star Forming Region ; Molecular clouds ; Carbon monoxide
Keywords: stars: formation - stars: evolution - Galaxy: structure -
ISM: bubbles - stars: massive
Abstract:
Star formation in the outer Galaxy is thought to be different from
that in the inner Galaxy, as it is subject to different environmental
parameters such as metallicity, interstellar radiation field, or mass
surface density, which all change with galactocentric radius.
Extending our star formation knowledge, from the inner to the outer
Galaxy, helps us to understand the influences of the change of the
environment on star formation throughout the Milky Way.
We aim to obtain a more detailed view on the structure of the outer
Galaxy, determining physical properties for a large number of star
forming clumps and understanding star formation outside the solar
circle. As one of the largest expanding Galactic super-shellsis
present in the observed region, a unique opportunity is taken here to
investigate the influence of such an expanding structure on
star formation as well.
We used pointed 12CO(2-1) observations conducted with the APEX
telescope to determine the velocity components towards 830 dust clumps
identified from 250um Herschel/Hi-GAL SPIRE emission maps in the outer
Galaxy between 225<l<260. We determined kinematic distances from the
velocity components, in order to analyze the structure of the outer
Galaxy and to estimate physical properties such as dust temperatures,
bolometric luminosities, clump masses, and H2 column densities for 611
clumps. Forthis, we determined the dust spectral energy density
distributions from archival mid-infrared to sub- millimeter (submm)
emission maps.
We find the identified CO clouds to be strongly correlated with the
highest column density parts of the Hiemission distribution, spanning
a web of bridges, spurs, and blobs of star forming regions between the
larger complexes, unveiling the complex three-dimensional structure of
the outer Galaxy in unprecedented detail. Using the physical
properties of the clumps, we find an upper limit of 6% (40 sources)
capable of forming high-mass stars. This is supported by the fact that
only two methanol Class II masers,or 34 known or candidate HII
regions, are found in the whole survey area, indicating an even lower
fraction that are able to form high-mass stars in the outer Galaxy. We
fail to find any correlation of the physical parameters of the
identified (potential) star forming regions with the expanding
supershell, indicating that although the shell organizes the
interstellar material into clumps, the properties of the latter are
unaffected.
Using the APEX telescope in combination with publicly available
Hi-GAL, MSX, and Wise continuum emission maps, we were able to
investigate the structure and properties of a region of the Milky Way
in unprecedented detail.
Description:
In order to extend our previous studies of the ISM and star formation
(Koenig et al., 2017, Cat. J/A+A/599/A139, Urquhart et al., 2018, Cat.
J/MNRAS/473/1059) to the outer Galaxy between 225°≤l≤260°;
we used Herschel/Hi-GAL 250um SPIRE continuum emission maps to select
a representative sample of more than 800 sources from a rudimentary
source catalog of more than 25000 extracted clumps using SExtracor
(Bertin & Arnouts, 1996A&AS..117..393B 1996A&AS..117..393B), giving positions and source
sizes for these clumps. We observed these sources in 12CO(2-1),
identifying 1248 clouds that consist of a total of 1383 individual
velocity components, for a total of 1090 positions, including
recovered off-positions.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 57 1408 CO(2-1) Components
table5.dat 52 1270 CO(2-1) clouds/complexes
table67.dat 152 611 Physical properties derived from dust continuum
SEDs (tables 6 and 7)
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See also:
J/A+A/599/A139 : ATLASGAL massive clumps dust characterization (Koenig+, 2017)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name Line of sight name (LoS) (GLLL.lll+BB.bbb)
17 I1 --- Complex [1/5] Number of cloud along LoS
19- 23 F5.1 km/s Vlsr [0.3/106.0] Line of sight velocity
25- 27 F3.1 km/s Width [0.1/3.1] Component emission width
29- 32 F4.1 K Tmax [0.1/22.0] Maximum temperature
34- 36 F3.1 K e_Tmax [0.1/8.5] Maximum temperature uncertainty
38- 42 F5.1 K.km/s aint [0.1/123.0] Integrated intensity
44- 47 F4.1 K.km/s e_aint [0.2/77.0] Integrated intensity uncertainty
49- 52 F4.1 kpc rhel [0.4/11.6] Heliocentric distance
54- 57 F4.1 kpc rgal [8.5/16.4] Galactocentric distance
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Name Line of sight name (LoS) (GLLL.lll+BB.bbb)
17 I1 --- Complex [1/5] Number of cloud along LoS
19 I1 --- m_Complex [1/5] Number of components
21- 25 F5.1 km/s Vlsr [0.3/106.0] Line of sight velocity
27- 30 F4.1 km/s Cwidth [1.0/49.6] Cloud emission width
32- 36 F5.1 K Tmax [0.1/22.0]? Maximum temperature
38- 40 F3.1 K e_Tmax [0.1/8.5] Maximum temperature uncertainty
42- 46 F5.1 K.km/s aintC [0.1/194.7]? Integrated intensity
48- 52 F5.1 K.km/s e_aintC [0.1/46.6]? Integrated intensity uncertainty
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Byte-by-byte Description of file: table67.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name Source name (GLLL.lll+BB.bbb)
17- 23 F7.3 deg GLON [225.01/260] Galactic longitude of peak
25- 30 F6.3 deg GLAT [-2.5/0.19] Galactic latitude of peak
32- 35 F4.1 kpc rhel [1.0/11.6] Heliocentric distance
37- 41 F5.1 arcsec dapp [42.5/200] Apperture diameter
43- 47 F5.3 pc rfwhm [0.02/1.79] Linear source radius
49- 58 A10 --- Class Classification
60- 63 F4.1 K Tdust [9.69/41.3] Dust temperature
65- 67 F3.1 K e_Tdust [0.1/8.31] Dust temperature uncertainty
69- 75 E7.2 --- tau Optical Depth
77- 83 E7.2 --- e_tau Depth uncertainty
85- 93 F9.3 Lsun Lbol [0.08/24000] Bolometric luminosity
95-103 F9.4 Lsun e_Lbol [0.0/2800] Bolometric luminosity uncertainty
105-112 F8.3 Msun Mass [0.02/1700] Mass
114-121 F8.4 Msun e_Mass [0.0/360] Mass uncertainty
123-129 E7.2 cm-2 NH2p H2 peak column density
131-137 E7.2 cm-2 e_NH2p H2 peak column density uncertainty
139-145 F7.3 Lsun/Msun L/M [0.06/150] Luminosity-to-Mass ratio
147-152 F6.3 Lsun/Msun e_L/M [0.01/57] Luminosity-to-Mass ratio uncertainty
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Acknowledgements:
This research made use of Astropy, a community-developed core Python
package for Astronomy (Astropy Collaboration et al. 2013) and the
Astropy affilate software package photutils. This research made use of
Montage, funded by the National Aeronautics and Space Administrations
Earth Science Technology Office, Computation Technologies Project,
under Cooperative Agreement Number NCC5-626 between NASA and the
California Institute of Technology. Montage is maintained by the
NASA/IPAC Infrared Science Archive. This publication also makes use of
data products from the Wide-field Infrared Survey Explorer, which is a
joint project of the University of California, LosAngeles, and the Jet
Propulsion Laboratory/California Institute of Technology,funded by the
National Aeronautics and Space Administration.
From Carsten Koenig, koenig(at)mpifr-bonn.mpg.de
(End) Patricia Vannier [CDS] 15-Jan-2021