J/ApJS/230/17 CO obs. of MCs in the Extreme Outer Galaxy region (Sun+, 2017)
Molecular clouds in the Extreme Outer Galaxy between l=34.75° to 45.25°.
Sun Y., Su Y., Zhang S.-B., Xu Y., Chen X.-P., Yang J., Jiang Z.-B.,
Fang M.
<Astrophys. J. Suppl. Ser., 230, 17-17 (2017)>
=2017ApJS..230...17S 2017ApJS..230...17S (SIMBAD/NED BibCode)
ADC_Keywords: Carbon monoxide ; Surveys ; Molecular clouds ; Milky Way
Keywords: Galaxy: structure; ISM: molecules; radio lines: ISM
Abstract:
We present the results of an unbiased CO survey in the Galactic range
of 34.75°≤l≤45.25° and -5.25°≤b≤5.25°, and the
velocity range beyond the Outer arm. A total of 168 molecular clouds
(MCs) are identified within the Extreme Outer Galaxy (EOG) region, and
31 of these MCs are associated with 13CO emission. However, none of
them show significant C18O emission under the current detection
limit. The typical size and mass of these MCs are 5pc and
3x103M☉, implying a lack of large and massive MCs in the EOG
region. Similar to MCs in the outer Galaxy, the velocity dispersions
of EOG clouds are also correlated with their sizes; however, they are
well displaced below the scaling relationship defined by the inner
Galaxy MCs. These MCs with a median Galactocentric radius of 12.6kpc
show very different distributions from those of the MCs in the Outer
arm published in our previous paper, while roughly following the Outer
Scutum-Centaurus arm defined by Dame & Thaddeus (2011ApJ...734L..24D 2011ApJ...734L..24D).
This result may provide robust evidence for the existence of the Outer
Scutum-Centaurus arm. The lower limit of the total mass of this
segment is about 2.7x105M☉, which is about one magnitude lower
than that of the Outer arm. The mean thickness of the gaseous disk is
about 1.45° or 450pc, and the scale height is about 1.27°, or
400pc above the b=0° plane. The warp traced by CO emission is very
obvious in the EOG region and its amplitude is consistent with the
predictions by other warp models using different tracers, such as
dust, HI, and stellar components of our Galaxy.
Description:
The observations in the Galactic range of 34.75°≤l≤45.25°
and -5.25°≤b≤5.25° were conducted during 2011 November to
2015 March using the 13.7m millimeter-wavelength telescope of the
Purple Mountain Observatory (PMO) in Delingha, China. The molecular
lines of 12CO(J=1-0) in the upper sideband, and 13CO(J=1-0) and
C18O(J=1-0) in the lower sideband were observed simultaneously.
A total of 174 molecular clouds (MCs) were identified, of which 168
MCs probably lie in the Extreme Outer Galaxy (EOG) region.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 83 174 Parameters of molecular clouds (MCs) derived
by 12CO(1-0)
table2.dat 19 23 Molecular clouds marginally detected by this study
table3.dat 64 35 Parameters of molecular clouds derived by 13CO(1-0)
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See also:
VII/114 : Massachusetts-Stony Brook Galactic Plane CO Survey (Clemens+ 1986)
VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Galactic HI (Kalberla+ 2005)
J/ApJS/63/821 : Inner Galaxy MCs and cloud cores (Scoville+, 1987)
J/A+A/275/67 : Velocity Field of the outer Galaxy (Brand+ 1993)
J/ApJ/551/852 : FCRAO CO survey of the outer Galaxy (Heyer+, 2001)
J/A+A/382/513 : Galaxy warps in the HDF North and South (Reshetnikov+, 2002)
J/ApJS/144/47 : Outer galaxy molecular cloud catalog (Brunt+, 2003)
J/A+A/397/133 : Star-forming complexes in the Galaxy (Russeil+, 2003)
J/PASJ/57/917 : CO MCs in southern Galactic Warp (Nakagawa+, 2005)
J/A+A/453/635 : Modelling Galactic Interstellar Extinction (Marshall+, 2006)
J/ApJ/686/948 : CO in extragalactic giant molecular clouds (Bolatto+, 2008)
J/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009)
J/ApJ/723/492 : Properties of GRS molecular clouds (Roman-Duval+, 2010)
J/A+A/569/A125 : Spiral structure of the Milky Way (Hou+, 2014)
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/224/7 : CO obs. of the outer arm in the 2nd quadrant (Du+, 2016)
J/ApJ/828/59 : Molecular clouds in the Milky Way with CO obs. (Su+, 2016)
J/ApJ/834/57 : MW molecular clouds from 12CO (Miville-Deschenes+, 2017)
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- 19 A13 --- MWISP Cloud identifier (GLL.lll+B.bbb) (1)
21- 22 A2 --- f_MWISP Flag on MWISP (2)
24- 28 F5.1 km/s VLSR [-74/-45] Local Standard of Rest
velocity (3)
30- 32 F3.1 km/s DelV [0.5/5.3] Line width Full-Width
at Half-Maximum (3)
34- 37 F4.1 K.km/s Int [1/21] Integrated 12CO intensity (3)
39- 41 F3.1 K Tpk [1/7] Peak intensity (3)
43- 46 F4.1 arcmin2 Area [0.9/27] Angular area defined by
3σ limits
48- 51 F4.1 kpc Dist [16.6/20] Heliocentric distance (4)
53- 56 F4.1 kpc R [11.6/14.1] Galactocentric distance (4)
58- 61 F4.1 kpc Z [-0.5/1.5] Vertical scale height (5)
63- 66 F4.1 pc Rad [1/15] Cloud radius after
beam deconvolution
68- 72 F5.1 10+2Msun Mass [1/139] Cloud mass (6)
74- 78 F5.1 10+2Msun Mvir [1/691] Virial mass
80- 83 F4.1 Msun/pc2 Sigma [5.5/29.2] Molecular gas surface density
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Note (1): Designated as MWISP (for CO survey project name: Milky Way Imaging
Scroll Painting) followed by the Galactic longitude and latitude
coordinates of the peak of the emission in degrees.
Note (2): Flag as follows:
* = Also listed in Su et al. (2016, J/ApJ/828/59).
d = Sources with VLSR>-1.6l+13.2km/s probably lie in the Outer arm.
Note (3): For the single Gaussian fitting results of the brightest
CO spectrum of the MCs.
Note (4): Assuming the rotation curve and Galactic parameters obtained
by Reid et al. (2014, J/ApJ/783/130).
Note (5): Defined by Z=Dist*sin(b) where b is the Galactic latitude.
Note (6): Calculated using X=2.0x1020cm-2 (K.km/s)-1
(Bolatto et al. 2013ARA&A..51..207B 2013ARA&A..51..207B).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Cloud identifier
15- 19 F5.1 km/s VLSR [-69/-48] Local Standard of Rest velocity
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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- 19 A13 --- MWISP Cloud identifier (GLL.lll+B.bbb)
21 A1 --- f_MWISP [t] t: sources belong to the same
cloud MWISP G37.175+0.792
23- 27 F5.1 km/s VLSR [-64/-45] Local Standard of Rest velocity (1)
29- 32 F4.2 km/s e_VLSR [0.04/0.2] VLSR uncertainty
34- 36 F3.1 km/s DelV [0.5/4.5] Line width Full-Width
at Half-Maximum (1)
38- 41 F4.2 km/s e_DelV [0.1/0.7] DelV uncertainty
43- 45 F3.1 K.km/s Int [0.3/2.8] Integrated 13CO intensity (1)
47- 50 F4.2 K.km/s e_Int [0.06/0.4] Int uncertainty
52- 54 F3.1 K Tpk [0.3/1.3] Peak intensity (1)
56- 59 F4.1 --- 12CO/13CO [2.8/14.3]? Integrated intensity ratio of
12C0 and 13CO
61- 64 F4.2 K rms [0.1/0.3] rms level of each detection with a
velocity resolution of 0.166km/s (2)
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Note (1): The single Gaussian fitting results of the brightest 13CO spectrum
of the molecular clouds.
Note (2): Those with values larger than 0.2K are the rms values of a single
pixel; otherwise, the rms was averaged over nine pixels.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 07-Aug-2017