J/ApJS/254/3 CO obs. of molecular clouds in the MW midplane (Ma+, 2021)
Molecular clouds in the second quadrant of the Milky Way midplane from
l=104.75° to l=119.75° and b=-5.25° to b=5.25°.
Ma Y., Wang H., Li C., Lin L., Sun Y., Yang J.
<Astrophys. J. Suppl. Ser., 254, 3 (2021)>
=2021ApJS..254....3M 2021ApJS..254....3M
ADC_Keywords: Molecular clouds; Carbon monoxide; Velocity dispersion;
Milky Way
Keywords: Interstellar medium ; Interstellar clouds ; Molecular clouds ;
Star formation ; Surveys
Abstract:
In this work, we study the properties of molecular clouds in the
second quadrant of the Milky Way Midplane, from l=104.75° to
l=119.75°, and b=-5.25° to b=5.25°, using the 12CO,
13CO, and C18O J=1-0 emission line data from the Milky Way Imaging
Scroll Painting project. We identify 857 and 300 clouds in the 12CO
and 13CO spectral cubes, respectively, using the DENDROGRAM + SCIMES
algorithms. The distances of the molecular clouds are estimated, and
physical properties such as the mass, size, and surface densities of
the clouds are tabulated. The molecular clouds in the Perseus Arm are
about 30-50 times more massive, and 4-6 times larger than the clouds
in the Local Arm. This result, however, is likely to be biased by
distance selection effects. The surface densities of the clouds are
enhanced in the Perseus Arm, with an average value of
∼100M☉/pc2. Here. we select the 40 most extended
(>0.35arcdeg2) molecular clouds from the 12CO catalog to build the
H2 column density probability distribution function (N-PDF). Some
78% of the N-PDFs of the selected molecular clouds are well fitted
with log-normal functions with only small deviations at high
densities, corresponding to star-forming regions with scales of ∼1-5pc
in the Local Arm, and ∼5-10pc in the Perseus Arm. About 18% of the
selected molecular clouds have power-law N-PDFs at high densities. In
these molecular clouds, the majority of the regions fitted with the
power law correspond to molecular clumps at sizes of ∼1pc, or
filaments at widths of ∼1pc.
Description:
We have observed the 12CO, 13CO, and C18O J=1-0 line emission
toward the Galactic plane, with a sky coverage of 15°x10°,
from l=104.75° to l=119.75°, and b=-5.25° to b=5.25°.
This observation is part of the Milky Way Imaging Scroll Painting
(MWISP) project, which is an unbiased simultaneous survey of the J=1-0
transitional emission of the three isotopologues of carbon monoxide
toward the Galactic plane, visible from the northern hemisphere.
Detailed observational information, together with the data processing
procedure for the MWISP project, have been comprehensively covered by
Su+ (2019ApJS..240....9S 2019ApJS..240....9S).
The observations were taken between 2012 March and 2018 October, using
the Purple Mountain Observatory (PMO) 13.7m millimeter-wavelength
telescope located at Delingha, China. The half-power beamwidth (HPBW)
of the telescope is around 52" and 50" at 110GHz and 115GHz,
respectively, and the pointing of the telescope has an accuracy of
about 5" for all observational epochs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 124 857 Properties of 12CO clouds
table3.dat 163 300 Properties of 13CO clouds
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See also:
VII/20 : Catalogue of HII Regions (Sharpless 1959)
VII/278 : A Catalogue of Galactic Supernova Remnants (Green 2017)
J/ApJ/428/693 : Rosette Nebula & Maddalena Cloud structures (Williams+ 1994)
J/ApJ/551/852 : FCRAO CO survey of the outer Galaxy (Heyer+, 2001)
J/ApJ/641/389 : Millimetric observations of IRDC cores (Rathborne+, 2006)
J/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009)
J/ApJ/723/492 : GRS molecular clouds physical data (Roman-Duval+, 2010)
J/MNRAS/416/1764 : H2O Southern Galactic Plane Survey (HOPS) (Walsh+, 2011)
J/MNRAS/431/1752 : ATLASGAL 6.7GHz methanol masers (Urquhart+, 2013)
J/ApJS/212/1 : The WISE catalog of Galactic HII regions (Anderson+, 2014)
J/ApJ/783/130 : Parallaxes of high mass star forming regions (Reid+, 2014)
J/A+A/575/A79 : SPIRE 250um maps of 4 molecular clouds (Schneider+, 2015)
J/ApJ/798/L27 : CO obs. of molecular clouds in the 2nd quadrant (Sun+, 2015)
J/ApJS/224/7 : CO obs. of the outer arm in the 2nd quadrant (Du+, 2016)
J/ApJ/834/57 : MW molecular clouds from 12CO (Miville-Deschenes+, 2017)
J/MNRAS/477/2220 : Larson relations in massive clumps (Traficante+, 2018)
J/ApJ/878/44 : 13CO clumps toward the Cas A supernova remnant (Ma+, 2019)
J/A+A/633/A147 : FQS. Galactic Plane CO survey (Benedettini+, 2020)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- --- [MWISP]
7- 28 A22 --- MWISP MWISP project source identifier (G1)
30- 36 F7.3 deg GLON [104.76/119.8] Centroid Galactic Longitude
38- 43 F6.3 deg GLAT [-5.2/5.3] Centroid Galactic Latitude
45- 48 I4 arcsec amaj [66/4721] Intensity-weighted major axis,
θa
50- 53 I4 arcsec bmin [26/2279] Intensity-weighted minor axis,
θb
55- 58 I4 deg PA [-179/179] Position Angle
60- 66 F7.2 km/s VLSR [-101.3/15.5] Local Standard of Rest velocity
68- 71 F4.2 km/s sigma [0.36/5.4] Velocity dispersion, σv
73- 76 F4.2 kpc Dist [0.19/9.6]? Heliocentric distance
78- 82 F5.2 pc Reff [0.06/38.5]? Effective Radius
84- 90 E7.2 cm-2 NH2 [2e+20/5.7e+21] Average column density,
N0(H2)
92-101 F10.2 Msun Mass [0.3/1.11e+6]? XCO mass
103-108 F6.2 Msun/pc2 Sigma [7.8/432]? Mass surface density, Σ
110-117 F8.2 cm-3 n [9/10166]? Number density
119-124 F6.2 --- aVir [0.4/345.2]? Virial parameter, αvir
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- --- [MWISP]
7- 28 A22 --- MWISP MWISP project source identifier (G1)
30- 36 F7.3 deg GLON [104.79/119.7] Centroid Galactic Longitude
38- 43 F6.3 deg GLAT [-4.5/5.2] Centroid Galactic Latitude
45- 48 I4 arcsec amaj [53/3138] Intensity-weighted major axis,
θa
50- 53 I4 arcsec bmin [28/1225] Intensity-weighted minor axis,
θb
55- 58 I4 deg PA [-179/178] Position Angle
60- 65 F6.2 km/s VLSR [-72/6.5] Local Standard of Rest velocity
67- 70 F4.2 km/s sigma [0.3/4.3] Velocity dispersion, σv
72- 75 F4.2 kpc Dist [0.2/6.2]? Heliocentric distance
77- 81 F5.2 pc Rad [0.12/20.9]? Effective Radius
83- 87 F5.2 K Tex [7.8/47]? Excitation temperature
89- 92 F4.2 --- Tau [0.2/1]? Optical depth
94-100 E7.2 cm-2 NH2 [8.2e+19/6.3e+23]? Average column density,
N0(H2)
102-111 F10.2 Msun Mass [1.1/1.6e+6]? LTE mass
113-119 F7.2 Msun/pc2 Sigma [12.4/1703.1]? Mass surface density, Σ
121-128 F8.2 cm-3 n [60/23307]? Number density
130-134 F5.2 --- aVir [0.1/99.4]? Virial parameter, αvir
136-140 A5 --- --- [MWISP]
142-163 A22 --- Match Identifier of matched MWISP 12CO clouds
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Global notes:
Note (G1): The source name is defined under the MWISP standard. According to
the MWISP standard for nomenclature, molecular clouds are named after
their centroid positions and velocities. Specifically, the names start
with "MWISP", followed by the spatial coordinates of the molecular
clouds, accurate to three decimal places, and their centroid
velocities, accurate to two decimal places. The accuracy is set based
on the pointing accuracy and velocity resolution of the PMO-13.7m
telescope.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 02-Jul-2021