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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 (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) 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 σ0v/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). 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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 345 8107 The molecular clouds catalog
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) : CO data online archive Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
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 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
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).
History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 04-May-2017
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