J/ApJ/852/2 CO emission from 78 WISE HII region in the OSC (Wenger+, 2018)
Carbon monoxide observations toward star-forming regions in the Outer
Scutum-Centaurus spiral arm.
Wenger T.V., Khan A.A., Ferraro N.G., Balser D.S., Armentrout W.P.,
Anderson L.D., Bania T.M.
<Astrophys. J., 852, 2-2 (2018)>
=2018ApJ...852....2W 2018ApJ...852....2W (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way; Carbon monoxide; Molecular data; Interstellar medium;
H II regions; Radio lines; Infrared sources
Keywords: Galaxy: structure; ISM: molecules; radio lines: ISM; surveys
Abstract:
The Outer Scutum-Centaurus arm (OSC) is the most distant molecular
spiral arm known in the Milky Way. The OSC may be the very distant end
of the well-known Scutum-Centaurus arm, which stretches from the end
of the Galactic bar to the outer Galaxy. At this distance the OSC is
seen in the first Galactic quadrant. The population of star formation
tracers in the OSC remains largely uncharacterized. Extragalactic
studies show a strong correlation between molecular gas and star
formation, and carbon monoxide (CO) emission was recently discovered
in the OSC. Here we use the Arizona Radio Observatory (ARO) 12m
telescope to observe the 12CO J=1-0 and 13CO J=1-0 transitions
toward 78 HII region candidates chosen from the WISE Catalog of
Galactic HII Regions. These targets are spatially coincident with the
Galactic longitude-latitude (l,b) OSC locus as defined by HI emission.
We detect CO emission in ∼80% of our targets. In total, we detect
117 12CO and 40 13CO emission lines. About two-thirds of our
targets have at least one emission line originating beyond the solar
orbit. Most of the detections beyond the solar orbit are associated
with the outer arm, but there are 17 12CO emission lines and
8 13CO emission lines with LSR velocities that are consistent with
the velocities of the OSC. There is no apparent difference between the
physical properties (e.g., molecular column density) of these OSC
molecular clouds and non-OSC molecular clouds within our sample.
Description:
We used the Arizona Radio Observatory (ARO) 12m telescope to observe
the 12CO (J=1-0) transition at 115.27120GHz toward 78 HII regions
and HII region candidates located in the first Galactic quadrant.
We observed the optically thin 13CO J=1-0 transition at 110.20132GHz
in a subset of targets.
Our observations were performed between 2016 February 11-16.
We detect 117 12CO spectral line components in 62 of 78 WISE HII
region candidates, and 40 13CO components in 27 of 30 targets.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 64 134 12CO emission line parameters
table2.dat 64 43 13CO emission line parameters
table3.dat 57 37 Molecular cloud properties
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See also:
VIII/54 : Atlas of Galactic Neutral Hydrogen (Hartmann+, 1997)
VIII/75 : HI survey of the sky DE<+25° (Bajaja+, 2005)
VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Galactic HI (Kalberla+ 2005)
J/A+A/275/67 : Velocity Field of the outer Galaxy (Brand+ 1993)
J/A+A/417/107 : CO velocities in southern HII regions (Russeil+, 2004)
J/ApJS/181/255 : CO in Galactic HII regions (Anderson+, 2009)
J/ApJ/754/62 : HRDS III. HII region kinematic distances (Anderson+, 2012)
J/ApJ/783/130 : Parallaxes of high mass star forming regions (Reid+, 2014)
J/ApJ/798/L27 : CO obs. of molecular clouds in the 2nd quadrant (Sun+, 2015)
J/ApJS/221/26 : Radio obs. of Galactic WISE HII regions (Anderson+, 2015)
J/ApJS/230/17 : CO obs. of MCs in the Extreme Outer Galaxy region (Sun+, 2017)
J/ApJ/841/121 : HII region cand. in the OSC spiral arm (Armentrout+, 2017)
Byte-by-byte Description of file: table[12].dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Target name (GLLL.lll+B.bbb)
15- 16 A2 --- m_Name Component on Name (1)
18 A1 --- f_Name [V] Flag on Name (2)
20- 24 F5.2 K TL [0.1/22.3]? The peak line intensity, TL
26- 29 F4.2 K e_TL [0/0.8]? TL 1σ uncertainty
31- 36 F6.2 km/s Vlsr [-89.1/72.5]? LSR velocity
38- 41 F4.2 km/s e_Vlsr [0/1.2]? Vlsr 1σ uncertainty
43- 46 F4.2 km/s DelV [0.66/6.6]? FWHM line width, ΔV
48- 51 F4.2 km/s e_DelV [0.01/2.81]? DelV 1σ uncertainty
53- 57 F5.3 K rms [0.009/0.06] The root-mean-square noise in
the line-free baseline
59- 62 F4.1 min Exp [9.7/78] The total integration time, tintg
64 A1 --- QF [A-D] Quality factor (A=best) (3)
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Note (1): For 12CO spectra with multiple emission components, we append
a letter at the end of the target name (a, b, c, etc.) in order of
decreasing line intensity.
Note (2): Flag as follows:
V = VLSR within the Outer Scutum-Centaurus arm (OSC) velocity range
defined by VLSR=-1.6l±15km/s
Note (3): We assigned a Quality Factor (A, B, or C) to every CO emission line.
This judgment was based on the signal-to-noise ratio and expected line
properties. Code as follows:
A = profiles with a signal-to-noise ratio larger than 10 with no
blending and flat spectral baselines
B = lower signal-to-noise ratio than A or some blending of lines. Here
the blending should not be so severe that the individual peaks could
not be visually detected.
C = remaining targets, which were often blended and more difficult to fit
D = spectra with no CO detections
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name 12CO component name (GLLL.lll+B.bbb)
15- 16 A2 --- m_Name Component on Name
18- 23 F6.2 km/s Vlsr [-84.81/6.87] LSR velocity
25- 29 F5.2 kpc Rgal [8.22/15.77] Galactocentric radius
31- 35 F5.2 kpc Dist [0.38/20.81] Distance from the Sun
37- 41 F5.2 kpc Dist2 [12.39]? Second value of distance (1)
43- 46 F4.2 K T12CO [0.99/9.6] 12CO line intensity
48- 51 F4.2 K T13CO [0.1/1.9] 13CO line intensity
53- 57 F5.2 10+20cm-2 NH2 [0.79/28.12] NH2 column density
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Note (1): Sources within the solar circle have two values for the distance
since we did not resolve the kinematic distance ambiguity.
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Nomenclature note:
WISE HII region candidates (see Anderson+ 2014, J/ApJS/212/1 ;
<[ABB2014] WISE GLLL.lll+BB.bbb> in Simbad) or
Armentrout+ 2017, J/ApJ/841/121
History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 22-Sep-2023