J/ApJ/828/59 Molecular clouds in the Milky Way with CO obs. (Su+, 2016)
The distant outer gas arm between l=35 and l=45.
Su Y., Sun Y., Li C., Zhang S., Zhou X., Fang M., Yang J., Chen X.
<Astrophys. J., 828, 59-59 (2016)>
=2016ApJ...828...59S 2016ApJ...828...59S (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Milky Way ; Radio lines ; Surveys
Keywords: Galaxy: structure; ISM: molecules; radio lines: ISM
Abstract:
The Galactic plane has been mapped from l=34.75° to 45.25° and
b=-5.25° to 5.25° in the CO (J=1-0) emission with the 13.7m
telescope of the Purple Mountain Observatory. The unbiased survey
covers a large area of 110 square degrees sampled every 30" with a
velocity resolution of ∼0.2km/s. In this paper, we present the result
of an unbiased CO survey of this longitude and latitude range in the
velocity range from -60 to -10km/s. Over 500 molecular clouds (MCs)
are picked out from the 12CO (J=1-0) emission, and 131 of these MCs
are associated with 13CO emission. The distant MCs, which lie beyond
the solar circle and are mostly concentrated in the Galactic plane,
trace the large-scale molecular gas structure over 10 degrees of
Galactic azimuth. We find that the distribution of the distant MCs can
be well fitted by a Gaussian function with a full width at half
maximum (FWHM) of 0.7° with the Galactic latitude. We suggest that
the CO emission of the segment is from the Outer Arm. The physical
mid-plane traced by the Outer Arm seems to be slightly displaced from
the IAU-defined plane on a large scale, which could be explained by
the warped plane at large Galactocentric distances of ≳10kpc and the
apparent tilted mid-plane to the projected IAU-defined plane caused by
the Sun's z-height above the disk for distances near and within the
Solar circle. After removing the effect of the warp and tilted
structure, the scale height of the MCs in the Outer Arm is about
0.6° or 160pc at a heliocentric distance of 15kpc. If the inner
plane of our Galaxy is flat, we can derive an upper limit of the Sun's
offset of ∼17.1pc above the physical mid-plane of the Milky Way. We
also discuss the correlations between the physical parameters of the
distant MCs, which is quite consistent with the result of other
studies of this parameter.
Description:
The Milky Way Imaging Scroll Painting (MWISP) project is a high
resolution (50") 12CO (J=1-0), 13CO (J=1-0), and C18O (J=1-0)
survey of the northern Galactic plane, performed with the Purple
Mountain Observatory Delingha 13.7m telescope. The survey started in
2011, and will cover Galactic longitudes from l=-10° to 250°
and latitudes from b=-5° to 5° over a period of ∼10 years.
We mapped ∼110 square degrees (439 cells) in the region between
Galactic longitudes 34.75-45.25° and latitudes -5.25° to
5.25° during 2011 November to 2015 March using the 13.7m
millimeter-wavelength telescope located at Delingha in China. The
molecular lines of 12CO (J=1-0), 13CO (J=1-0), and C18O (J=1-0)
were observed simultaneously with the On-The-Fly (OTF) method.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 53 575 Parameters of 575 molecular clouds identified
from 12CO(J=1-0) emission
table2.dat 53 131 Parameters of 131 molecular clouds identified
from 13CO(J=1-0) emission
table3.dat 91 28 Molecular clouds associated with massive
star formation regions
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See also:
VIII/40 : GB6 catalog of radio sources (Gregory+ 1996)
VIII/58 : A Survey of Radio H II Regions in the Northern Sky (Lockman+ 1989)
VIII/39 : Composite CO Survey of the Milky Way (Dame+ 1987)
J/ApJS/224/7 : CO obs. of the outer arm in the 2nd quadrant (Du+, 2016)
J/ApJS/221/26 : Radio obs. of Galactic WISE HII regions (Anderson+, 2015)
J/ApJ/798/L27 : CO obs. of molecular clouds in the 2nd quadrant (Sun+, 2015)
J/ApJ/783/130 : Parallaxes of high mass star forming regions (Reid+, 2014)
J/AJ/147/46 : Properties of clumps in the NAN complex (Zhang+, 2014)
J/ApJ/738/27 : Galactic HII regions RRL and continuum data (Balser+, 2011)
J/ApJS/194/32 : The HII Region Discovery Survey (HRDS). II. (Anderson+, 2011)
J/ApJ/723/492 : Properties of GRS molecular clouds (Roman-Duval+, 2010)
J/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009)
J/A+A/382/513 : Galaxy warps in the HDF North and South (Reshetnikov+, 2002)
J/ApJ/551/852 : FCRAO CO survey of the outer Galaxy (Heyer+, 2001)
J/A+AS/115/81 : A CS(2-1) survey of UC HII regions (Bronfman+, 1996)
J/A+A/275/67 : Velocity Field of the outer Galaxy (Brand+ 1993)
J/ApJS/63/821 : Inner Galaxy Molecular clouds & cloud cores (Scoville+, 1987)
http://www.radioast.nsdc.cn/mwisp.php : MWISP home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I03 --- Seq Running index number
5- 10 F6.3 deg GLON Galactic longitude
12- 17 F6.3 deg GLAT Galactic latitude
19- 24 F6.2 km/s VLSR [-57/-10] Local Standard of Rest velocity
26- 29 F4.2 km/s VFWHM [0.3/7] Full Width at Half Maximum
of VLSR
31- 34 F4.2 K Tpeak [1.8/10] Peak temperature
36- 40 F5.2 arcmin2 Area [0.6/45.3] Area
42- 46 F5.2 K.km/s W12CO [0.5/14.4] Integrated 12CO emission
line flux
48- 53 F6.2 K.km/s.arcmin2 L12CO [1/223] The 12CO luminosity
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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- 3 I03 --- Seq Running index number
5- 10 F6.3 deg GLON Galactic longitude
12- 17 F6.3 deg GLAT Galactic latitude
19- 24 F6.2 km/s VLSR [-53/-10] Local Standard of Rest velocity
26- 29 F4.2 km/s VFWHM [0.4/5.1] Full Width at Half Maximum
of VLSR
31- 34 F4.2 K Tpeak [0.8/3] Peak temperature
36- 40 F5.2 arcmin2 Area [0.6/7.2] Area
42- 46 F5.2 K.km/s W13CO [0.3/5] Integrated 13CO emission
line flux
48- 53 F6.2 K.km/s.arcmin2 L13CO [0.4/35] The 13CO luminosity
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- --- [MWISP]
7- 21 A15 --- MWISP Molecular cloud (MC) name (GLLL.lll+BB.bbb)
from the 13CO (J=1-0) emission (table 2)
23 A1 --- f_MWISP e: from the 12CO (J=1-0) emission (table 1)
25- 30 F6.3 deg GLON MC Galactic longitude
32- 37 F6.3 deg GLAT MC Galactic latitude
39- 44 F6.2 km/s Vel [-51/-12] MC LSR velocity (from table 2 or 1)
46- 65 A20 --- Tracer Tracer designation (1)
67- 72 F6.3 deg GTLAT ? Tracer Galactic longitude (1)
74- 79 F6.3 deg GTLON ? Tracer Galactic latitude (1)
81- 86 F6.2 km/s VLSR [-55.1/-10.5]? LSR velocity (1)
87 A1 --- f_VLSR [f] Flag on VLSR (2)
89- 91 A3 --- Ref Reference(s) (3)
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Note (1): We use HII regions and 6.7GHz methanol masers to trace massive star
formation regions. The position and the velocity of the HII region is
from the radio continuum emission and the radio recombination line,
respectively. The position and the velocity of the 6.7 GHz maser is
from the observations of the maser survey (Green & McClure-Griffiths
2011MNRAS.417.2500G 2011MNRAS.417.2500G; Breen+ 2015MNRAS.450.4109B 2015MNRAS.450.4109B).
Based on Tables 1 and 2, we do not find the CO counterpart of the
6.7GHZ maser G38.565+0.538 with the LSR velocity of -28.8km/s
(Table 1 in Breen+ 2015MNRAS.450.4109B 2015MNRAS.450.4109B). However, a point-like MC with
a temperature of ∼1.5K and the LSR velocity of -35.40km/s is detected
from the 12CO (J=1-0) data at the maser's position.
Note (2):
f = The velocity of the HII region is from the CS (J=2-1) observation.
Note (3): Reference as follows:
1 = Lockman (1989, VIII/58),
2 = Bronfman et al. (1996, J/A+AS/115/81),
3 = Gregory et al. (1996, VIII/40),
4 = Anderson et al. (2011, J/ApJS/194/32),
5 = Balser et al. (2011, J/ApJ/738/27),
6 = Green & McClure-Griffiths (2011MNRAS.417.2500G 2011MNRAS.417.2500G),
7 = Bania et al. (2012ApJ...759...96B 2012ApJ...759...96B),
8 = Anderson et al. (2015, J/ApJS/221/26),
9 = Breen et al. (2015MNRAS.450.4109B 2015MNRAS.450.4109B).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 06-Dec-2016