J/ApJS/262/16 Column density maps for MWISP 13CO mol. clouds (Ma+, 2022)
Gas column density distribution of molecular clouds in the third quadrant of
the Milky Way.
Ma Y., Wang H., Zhang M., Wang C., Zhang S., Liu Y., Li C., Zheng Y.,
Yuan L., Yang Ji
<Astrophys. J. Suppl. Ser., 262, 16 (2022)>
=2022ApJS..262...16M 2022ApJS..262...16M
ADC_Keywords: Molecular clouds; Interstellar medium; Surveys; Carbon monoxide;
Molecular data; Milky Way
Keywords: Star formation ; Interstellar medium ; Interstellar clouds ;
Surveys ; Molecular clouds
Abstract:
We have obtained column density maps for an unbiased sample of
120 molecular clouds in the third quadrant of the Milky Way midplane
(b≤|5|°) within the Galactic longitude range from 195° to
225°, using the high-sensitivity 12CO and 13CO (J=1-0) data
from the Milky Way Imaging Scroll Painting (MWISP) project. The
probability density functions of the molecular hydrogen column density
of the clouds, N-pdfs, are fitted with both a lognormal (LN) function
and a lognormal plus power-law (LN+PL) function. The molecular clouds
are classified into three categories according to their shapes of
N-pdfs, i.e., LN, LN+PL, and UN (unclear). About 72% of the molecular
clouds fall into the LN category, while 18% and 10% fall into the
LN+PL and UN categories, respectively. A PL scaling relation,
σs∝NH20.44, exists between the width of the N-pdf,
σs, and the average column density, NH2, of the molecular
clouds. However, σs shows no correlation with the mass of the
clouds. A correlation is found between the dispersion of normalized
column density, σN/<N>, and the sonic Mach number, M, of
molecular clouds. Overall, as predicted by numerical simulations, the
N-pdfs of the molecular clouds with active star formation activity
tend to have N-pdfs with PL high-density tails.
Description:
The 12CO and 13CO data used in this work are part of the Milky Way
Imaging Scroll Painting (MWISP) survey. Su+ (2019ApJS..240....9S 2019ApJS..240....9S) have
given a detailed introduction to the observations and the data
reduction processes of the project. In the MWISP project, the 12CO,
13CO, and C18O J=1-0 spectra are obtained simultaneously using the
nine-beam Superconducting Spectroscopic Array Receiver (SSAR) equipped
on the Purple Mountain Observatory (PMO) 13.7m telescope. The
spectrometer on the PMO 13.7m telescope has 16,384 velocity channels
with a total bandwidth of 1GHz, which provides a velocity resolution
of 0.17km/s at 110GHz.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 141 120 Properties of the probability density functions
of the molecular hydrogen column density (N-pdfs)
and physical parameters of the molecular clouds
fig/* . 120 Individual N-pdfs in JPG format
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See also:
II/360 : Gaia DR2 x AllWISE catalogue (Marton+, 2019)
VII/20 : Catalogue of HII Regions (Sharpless 1959)
VII/284 : A Catalogue of Galactic Supernova Remnants (Green, 2019)
J/ApJ/551/852 : FCRAO CO survey of the outer Galaxy (Heyer+, 2001)
J/A+A/487/993 : MAMBO Mapping of c2d Clouds and Cores (Kauffmann+, 2008)
J/A+A/560/A24 : IRAM 30m CO-observations in W43 (Carlhoff+, 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/578/A29 : Column density maps in 4 IRDCs (Schneider+, 2015)
J/MNRAS/458/3479 : SVM selection of WISE YSO Candidates (Marton+, 2016)
J/ApJ/834/57 : MW molecular clouds from 12CO (Miville-Deschenes+, 2017)
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)
J/ApJS/254/3 : CO obs. of molecular clouds in the MW midplane (Ma+, 2021)
J/ApJS/257/51 : Morphologies of MWISP 12CO mol. Clouds (Yuan+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- --- [MWISP]
7- 28 A22 --- MWISP MWISP designation (GLLL.lll+BB.bbb+vvv.vv) (1)
30- 33 A4 kpc Dist Distance of the cloud
35- 40 F6.3 --- mu [-1.74/0.65]? Fit parameter, µ,
of the N-pdfs in Equations 5-6 (Section 3.2.1)
42- 46 F5.3 --- sigS [0.58/2.63]? Fit parameter, σS,
of the N-pdfs in Equations 5-6 (Section 3.2.1)
48- 52 F5.3 --- br [0.26/1.9]? Fit parameter, br,
of the N-pdfs in Equations 5-6 (Section 3.2.1)
54- 59 F6.3 --- a [-7.97/-1.41]? Fit parameter, a,
of the N-pdfs in Equations 5-6 (Section 3.2.1)
61- 65 I5 --- Npix [163/77828] Pixel number
67- 71 F5.2 K Tpk [7.3/41.1] Peak excitation temperature
73- 79 E7.3 cm-2 NH2 [2e+20/3.4e+21] Average column density (2)
81- 85 F5.2 pc Rad [0.35/26.1]? Radius
87- 91 I5 Msun Mass [0/50552]? LTE mass
93- 98 F6.3 --- Skew [-0.58/0.74] skewness of the N-pdf
100- 105 F6.3 --- Kurt [-1.17/0.25] kurtosis of the N-pdf
107- 111 F5.3 --- tau [0.17/0.52] 13CO optical depth of the cloud
113- 117 F5.2 --- M [0.68/37.7] Mach number (3)
119- 122 I4 --- Nyso [0/1097] Number of associated YSOs
124- 129 F6.2 --- aVir [0.58/463]? Virial parameter (4)
131- 135 A5 --- Shape Category of the N-pdf (5)
137- 141 A5 --- Fig Figure number; column added by CDS
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Note (1): The source name is defined under the Milky Way Imaging Scroll
Painting (MWISP; Su+ 2019ApJS..240....9S 2019ApJS..240....9S) standard. According to the
MWISP standard for nomenclature, molecular clouds are named after
their centroid positions and velocities. Specifically, the names start
with "MWISP" and then contain the spatial coordinates of the molecular
clouds accurate to three decimal places and the centroid velocities
accurate to two decimal places. The accuracy is set according to the
pointing accuracy and the velocity resolution of the PMO 13.7m telescope.
Note (2): The average column density for each cloud is calculated above the
reference detection limit of the cloud.
Note (3): The Mach number, M, is defined as the ratio between the nonthermal
velocity dispersion and the local sound speed of the cloud. See Section 3.1.
Note (4): the virial parameter can be calculated according to
αvir=5σv2R/(GMLTE), where G is the gravitational
constant. See Section 3.1
Note (5): Category of N-pdf (probability density function of the molecular
hydrogen column density of the cloud) as follows:
LN = lognormal function (68 occurrences; see Figure 16)
LN+PL = lognormal plus power-law function (22 occurrences; see Figure 17)
UN = unclear (12 occurrences; see Figure 18)
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 16-Nov-2022