J/ApJ/798/L27 CO obs. of molecular clouds in the 2nd quadrant (Sun+, 2015)
A possible extension of the Scutum-Centaurus Arm into the outer second quadrant.
Sun Y., Xu Y., Yang J., Li F.-C., Du X.-Y., Zhang S.-B., Zhou X.
<Astrophys. J., 798, L27 (2015)>
=2015ApJ...798L..27S 2015ApJ...798L..27S
ADC_Keywords: Molecular clouds ; Milky Way ; Radio lines
Keywords: Galaxy: structure; ISM: molecules; radio lines: ISM
Abstract:
Combining H I data from the Canadian Galactic Plane Survey and CO data
from the Milky Way Imaging Scroll Painting project (MWISP), we have
identified a new segment of a spiral arm between Galactocentric radii
of 15 and 19kpc that apparently lies beyond the Outer Arm in the
second Galactic quadrant. Over most of its length, the arm is
400-600pc thick in z. The new arm appears to be the extension of the
distant arm recently discovered by Dame & Thaddeus (2011ApJ...734L..24D 2011ApJ...734L..24D)
as well as the Scutum-Centaurus Arm into the outer second quadrant.
Our current survey identified a total of 72 molecular clouds with
masses on the order of 102-104M☉ that probably lie in the
new arm. When all of the available data from the CO molecular clouds
are fit, the best-fitting spiral model gives a pitch angle of
9.3°±0.7°.
Description:
The observations were conducted during 2011 and 2014 using the 13.7m
telescope of the Purple Mountain Observatory (PMO) in Delingha, China.
The 12CO, 13CO, and C18O lines were observed simultaneously.
The 21cm line data were retrieved from the Canadian Galactic Plane
Survey (CGPS; Taylor et al. 2003, Cat. VI/128).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 72 72 Parameters of molecular clouds derived by CO(1-0)
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See also:
VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Galactic HI (Kalberla+ 2005)
VI/128 : Log of CGPS exposures (Taylor+, 2003-)
J/ApJS/196/18 : CO survey of galactic molecular clouds. II. (Bieging+, 2011)
J/A+A/470/161 : UBV photometry of HII regions exciting stars (Russeil+, 2007)
J/A+A/399/1083 : Outer Galaxy IRAS sources and 12CO emission (Kerton+, 2003)
J/ApJS/144/47 : Outer galaxy molecular cloud catalog (Brunt+, 2003)
J/A+A/397/133 : Star-forming complexes in the Galaxy (Russeil+, 2003)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1/72] Running sequence number
4- 6 A3 --- r_Seq Detections of the source (1)
8- 14 F7.3 deg GLON Galactic longitude of the CO emission peak
16- 21 F6.3 deg GLAT Galactic latitude of the CO emission peak
23- 28 F6.1 km/s Vlsr [-121/-74] LSR velocity of the CO line
30- 32 F3.1 K Tpk [1.3/8] CO peak temperature
34- 36 F3.1 km/s dV [0.7/3.3] The CO line width ΔV
38- 41 F4.1 K.km/s WCO [1.6/18] CO integrated intensity
43- 47 F5.1 arcmin2 Area [3/114] Angular area of the complex defined
by the 3σ limit
49- 52 F4.1 kpc Dist [9/15] Heliocentric distance (d) (2)
54- 57 F4.1 kpc R [14/22] Galactocentric distance (R) (2)
59- 62 F4.1 kpc Zsc [-0.4/0.8] Scale height (z=Dsin(b))
64- 67 F4.1 pc Rad [2.6/19.5] Cloud radius (3)
69- 72 F4.1 10+3Msun Mass [0.2/60.5] Cloud mass (4)
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Note (1): Flag as follows:
b = Source detected by Brunt et al. (2003, J/ApJS/144/47;
<[BKP2003] NNNNN> in Simbad)
d = Source detected by Digel et al. (1994ApJ...422...92D 1994ApJ...422...92D;
<[DDT94] Cloud Na> in Simbad)
Note (2): The heliocentric distance, d, and the Galactocentric distance, R,
respectively; both are derived from the rotation curve of Reid et al.
(2014ApJ...783..130R 2014ApJ...783..130R), assuming R☉=8.34kpc and
Θ0=240km/s.
Note (3): Equivalent radius of the molecular clouds corrected by the beam size
of the telescope.
Note (4): Cloud mass calculated using X=1.8x1020
(Dame et al. 2001ApJ...547..792D 2001ApJ...547..792D).
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 08-Jun-2015