J/ApJ/834/57 Milky Way molecular clouds from 12CO (Miville-Deschenes+, 2017)
Physical properties of molecular clouds for the entire Milky Way disk.
Miville-Deschenes M.-A., Murray N., Lee E.J.
<Astrophys. J., 834, 57-57 (2017)>
=2017ApJ...834...57M 2017ApJ...834...57M (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Carbon monoxide ; Galactic plane ;
Interstellar medium
Keywords: Galaxy: general; ISM: clouds; ISM: general;
ISM: kinematics and dynamics; methods: data analysis; turbulence
Abstract:
This study presents a catalog of 8107 molecular clouds that covers the
entire Galactic plane and includes 98% of the 12CO emission observed
within b±5°. The catalog was produced using a hierarchical
cluster identification method applied to the result of a Gaussian
decomposition of the Dame+ (2001ApJ...547..792D 2001ApJ...547..792D) data. The total H2
mass in the catalog is 1.2x109M☉, in agreement with previous
estimates. We find that 30% of the sight lines intersect only a single
cloud, with another 25% intersecting only two clouds. The most
probable cloud size is R∼30pc. We find that M∝R2.2±0.2,
with no correlation between the cloud surface density, Σ, and R.
In contrast with the general idea, we find a rather large range of
values of Σ, from 2 to 300M☉/pc2, and a systematic
decrease with increasing Galactic radius, Rgal. The cloud velocity
dispersion and the normalization σ0=σv/R1/2 both
decrease systematically with Rgal. When studied over the whole
Galactic disk, there is a large dispersion in the line width-size
relation and a significantly better correlation between σv and
ΣR. The normalization of this correlation is constant to better
than a factor of two for Rgal<20kpc. This relation is used to
disentangle the ambiguity between near and far kinematic distances. We
report a strong variation of the turbulent energy injection rate. In
the outer Galaxy it may be maintained by accretion through the disk
and/or onto the clouds, but neither source can drive the 100 times
higher cloud-averaged injection rate in the inner Galaxy.
Description:
The data set used here is that of Dame+ (2001ApJ...547..792D 2001ApJ...547..792D). Those
authors combined observations obtained over a period of 20yr with two
telescopes, one in the north (first located in New York City and then
in Cambridge, Massachusetts) and one in the south (Cerro Tololo,
Chile). These 1.2m telescopes have an angular resolution of ∼8.5' at
115GHz, the frequency of the 12CO 1-0 line. For the current study we
used the data set covering the whole Galactic plane with ±5° in
Galactic latitude.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 345 8107 The molecular clouds catalog
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See also:
VIII/39 : Composite CO Survey of the Milky Way (Dame+ 1987)
J/ApJ/833/229 : Star forming cloud-GMC complexes (Lee+, 2016)
J/A+A/590/A131 : Giant molecular filaments in the MW (Abreu-Vicente+, 2016)
J/ApJ/738/27 : Galactic HII regions RRL and continuum data (Balser+, 2011)
J/ApJ/734/65 : CI radial velocities with HST/STIS (Jenkins+, 2011)
J/ApJ/723/492 : Properties of GRS molecular clouds (Roman-Duval+, 2010)
J/ApJS/184/1 : Molecular clouds in the LMC by NANTEN. II. (Kawamura+, 2009)
J/ApJ/699/1153 : Kinematic dist. to GRS molecular clouds (Roman-Duval+, 2009)
J/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009)
J/ApJS/182/131 : Molecular clouds and clumps in the GRS (Rathborne+, 2009)
J/ApJ/686/948 : CO in extragalactic giant molecular clouds (Bolatto+, 2008)
J/ApJS/144/47 : Outer galaxy molecular cloud catalog (Brunt+, 2003)
J/ApJ/582/756 : Velocities of HII regions (Kolpak+, 2003)
J/ApJ/551/852 : FCRAO CO survey of the outer Galaxy (Heyer+, 2001)
J/A+A/275/67 : Velocity Field of the outer Galaxy (Brand+ 1993)
http://www.cfa.harvard.edu/rtdc/CO/ : CO data online archive
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Cloud [1/8107] Cloud number
6- 8 I3 --- Ncomp [5/600] Number of Gaussian components
10- 12 I3 --- Npix [5/444] Number of pixels on the sky
14- 25 E12.6 deg2 Area [0.07/7] Angular area
27- 39 E13.6 deg GLON [-179/180] Baricentric Galactic longitude
41- 52 E12.6 deg Sigb [0.1/1.5] Standard deviation in GLON
(σl)
54- 66 E13.6 deg GLAT [-5.2/5] Baricentric Galactic latitude
68- 79 E12.6 deg Sigl [0.1/1.2] Standard deviation in GLAT
(σb)
81- 93 E13.6 deg theta ?=0 Angle with respect to b=0
95-106 E12.6 K.km/s WCO [2/13929] Integrated CO emission
108-119 E12.6 cm-2 NH2 Average column density
121-132 E12.6 Msun/pc2 Sigma [1.8/739] Surface density
134-146 E13.6 km/s Vcent [-188/185] Centroid velocity
148-159 E12.6 km/s SigV [0.09/17] Velocity standard deviation
(σV)
161-172 E12.6 deg Rmax [0.1/3] Largest eigenvalue of the
inertia matrix
174-185 E12.6 deg Rmin [0.1/1.5] Smallest eigenvalue of the
inertia matrix
187-198 E12.6 deg Rang [0.1/1.7] Angular size
200-211 E12.6 kpc Rgal [0.003/97] Galacto-centric radius
213 I1 --- INF Near or far distance flag (0=near; 1=far) (1)
215-226 E12.6 kpc Dnear [0.001/88.5] Near kinematic distance
228-239 E12.6 kpc Dfar [0.01/88.5] Far kinematic distance
241-253 E13.6 kpc znear [-2.8/1.6] Near distance to Galactic mid-plane
255-267 E13.6 kpc zfar [-2.8/1.6] Far distance to Galactic mid-plane
269-280 E12.6 pc2 Snear [/744960] Near derived physical area
282-293 E12.6 pc2 Sfar [0.003/744960] Far derived physical area
295-306 E12.6 pc Rnear [0.008/470] Near derived physical size
308-319 E12.6 pc Rfar [0.03/470] Far derived physical size
321-332 E12.6 Msun Mnear [0.0003/] Near derived mass
334-345 E12.6 Msun Mfar [0.01/] Far derived mass
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Note (1): The index INF gives an estimate of which distance is more likely
based on the σv-ΣR relation
(σv=0.23(ΣR)0.43±0.14; Eq. 26).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 04-May-2017