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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 (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). 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:
FileName Lrecl Records Explanations
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)
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
Bytes Format Units Label Explanations
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 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
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 ( (Bolatto et al. 2013ARA&A..51..207B).
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 13 A13 --- Name Cloud identifier 15- 19 F5.1 km/s VLSR [-69/-48] Local Standard of Rest velocity
Byte-by-byte Description of file: table3.dat
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 Int [0.3/2.8] Integrated 13CO intensity (1) 47- 50 F4.2 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)
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.
History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 07-Aug-2017
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