J/ApJ/831/67 Galactic CHaMP. III. 12CO dense clump properties (Barnes+, 2016)
The Galactic Census of High- and Medium-mass Protostars. III. 12CO maps and physical properties of dense clump envelopes and their embedding GMCs. Barnes P.J., Hernandez A.K., O'Dougherty S.N., Schap III W.J., Muller E. <Astrophys. J., 831, 67-67 (2016)> =2016ApJ...831...67B (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Radio lines ; Velocity dispersion ; Molecular clouds ; Surveys ; Millimetric/submm sources Keywords: astrochemistry; ISM: molecules; radio lines: ISM; stars: formation Abstract: We report the second complete molecular line data release from the Census of High- and Medium-mass Protostars (CHaMP), a large-scale, unbiased, uniform mapping survey at sub-parsec resolution, of millimeter-wave line emission from 303 massive, dense molecular clumps in the Milky Way. This release is for all 12CO J=1->0 emission associated with the dense gas, the first from Phase II of the survey, which includes 12CO, 13CO, and C18O. The observed clump emission traced by both 12CO and HCO+ (from Phase I) shows very similar morphology, indicating that, for dense molecular clouds and complexes of all sizes, parsec-scale clumps contain Ξ∼75% of the mass, while only 25% of the mass lies in extended (≳10pc) or "low density" components in these same areas. The mass fraction of all gas above a density of 109m-3 is ξ9≳50%. This suggests that parsec-scale clumps may be the basic building blocks of the molecular interstellar medium, rather than the standard giant molecular cloud (GMC) concept. Using 12CO emission, we derive physical properties of these clumps in their entirety, and compare them to properties from HCO+, tracing their denser interiors. We compare the standard X-factor converting I12^CO_ to NH2 with alternative conversions, and show that only the latter give whole-clump properties that are physically consistent with those of their interiors. We infer that the clump population is systematically closer to virial equilibrium than when considering only their interiors, with perhaps half being long-lived (10s of Myr), pressure-confined entities that only terminally engage in vigorous massive star formation, supporting other evidence along these lines that was previously published. Description: In Phase II of the Mopra observing for the Census of High- and Medium-mass Protostars (CHaMP) project during 2009-12, we tuned the receiver to a central frequency of 111.3GHz and set up the Mopra Spectrometer (MOPS) digital filterbank to map all the CHaMP clumps in a second set of spectral lines at frequencies of 107-115GHz. This new set of transitions most notably includes the J=1->0 lines for the triad of CO-isotopologue species, 12CO, 13CO, and C18O. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 117 312 CHaMP clumps 12CO J=1->0 observed parameters table2.dat 90 272 CHaMP clumps 12CO J=1->0 physical parameters with standard NH2 conversion table3.dat 90 272 CHaMP clumps 12CO J=1->0 physical parameters with ThrUMMS NH2 conversion
See also: J/ApJ/780/173 : Masses of giant molecular clouds in Milky Way (Battisti+, 2014) J/ApJ/779/79 : Galactic CHaMP. II. Dense gas clumps. (Ma+, 2013) J/ApJ/777/157 : 90GHz obs. of high-mass star-forming regions (Hoq+, 2013) J/ApJS/196/12 : First results from Mopra HCO+ maps (Barnes+, 2011) J/ApJ/723/492 : Properties of GRS molecular clouds (Roman-Duval+, 2010) http://www.astro.ufl.edu/~peterb/research/thrumms/ : Three-mm Ultimate Mopra Milky Way Survey (ThrUMMS) home page Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 3 I3 --- BYF BYF number from Paper I (Barnes+, 2011, J/ApJS/196/12) 4- 5 A2 --- m_BYF Subclump letter from Paper I (1) 7- 13 F7.3 deg GLONp ? Galactic longitude, emission peak 15- 20 F6.3 deg GLATp ? Galactic latitude, emission peak 22 A1 --- opos Flag on 12CO observation (2) 24- 29 F6.2 K.km/s I12CO [5/262]? 12CO J=1->0 integrated intensity, I(12CO)=integral(T*RdV) 31- 34 F4.2 K.km/s e_I12CO [0.2/2]? Uncertainty in I12CO 36- 41 F6.2 km/s bVel [-45/3] Lower velocity range used for moment calculations 43- 49 F7.3 km/s BVel [-35/27] Upper velocity range used for moment calculations 51- 54 F4.1 K Tp [4/34]? Peak brightness temperature 56- 58 F3.1 K e_Tp [0.4/1.1]? Uncertainty in Tp 60- 65 F6.2 km/s Vlsr [-41/20]? Intensity-weighted LSR velocity 67- 69 F3.2 km/s e_Vlsr [0.06/1]? Uncertainty in Vlsr 71- 74 F4.2 km/s SigV [0.4/6.6]? Velocity dispersion 76- 78 F3.2 km/s e_SigV [0.06/1]? Uncertainty in SigV 80 A1 --- l_amaj Limit flag on amaj 81- 83 I3 arcsec amaj [34/831]? Major axis size, 2D decomposition 85- 86 I2 arcsec e_amaj ? Uncertainty in amaj 88 A1 --- l_bmin Limit flag on bmin 89- 91 I3 arcsec bmin [24/479]? Minor axis size, 2D decomposition 93- 94 I2 arcsec e_bmin [12/24]? Uncertainty in bmin 96- 98 I3 deg PA ? Position angle, 2D decomposition 100 I1 deg e_PA ? Uncertainty in PA 102 A1 --- epos Flag on 2D elliptical gaussian decomposition (2) 104-110 F7.3 deg GLONc ? Galactic longitude, emission centroid 112-117 F6.3 deg GLATc ? Galactic latitude, emission centroid
Note (1): Clumps which appear blended in 12CO, compared to HCO+, are listed as "ab" or "cd". Note (2): Flag on 12CO observation and gaussian decomposition: N = Clumps for which either a) no emission was seen and rms values are given for W12CO and Tp, or b) the HCO+ clump which fell off the mapped area and no rms values are given; W = Positions or sizes for these clumps were very indeterminate, due to their proximity to other (often brighter) clumps. In such cases line emission parameters are estimated in the appropriate location.
Byte-by-byte Description of file: table.dat
Bytes Format Units Label Explanations
1- 3 I3 --- BYF BYF number from Paper I (Barnes+, 2011, J/ApJS/196/12) 4- 5 A2 --- m_BYF Subclump letter from Paper I 7- 9 F3.1 kpc Dist [1/7] Final distance (1) 11 A1 --- f_Dist Flag on Dist (2) 13- 20 E8.2 m-2 NCO Peak column density in 12CO J=1->0 22- 27 F6.1 Msun/pc2 Sigp [17/3233] Mass surface density 29- 32 F4.2 pc Rad [0.1/7.2] Clump radius 34- 41 E8.2 Msun/pc3 rcol Equivalent mass density 43- 48 F6.1 m-3 ncol [4/1264] Estimated density at the emission peak 50- 54 I5 Msun Mcol [7/58792] LTE mass 56- 61 F6.2 pPa Pgas [0.3/925] Implied central gas pressure 63- 70 F8.3 K.km/s/pc2 LCO [2/4807] Peak line luminosity, 12CO J=1->0 72- 77 F6.2 --- alpha [0.3/209] Virial α parameter (α=Mvir/Mcol) 79- 82 F4.2 pc RJe [0.1/1.3] Rayleigh-Jeans radius 84- 90 I7 Msun MBE [52/232539] Bonnor-Ebert mass
Note (1): Distances are taken from Paper I, Barnes+ (2011, J/ApJS/196/12 and references therein). Note (2): Flag as follows: c = literature-based value; n = near kinematic; f = far kinematic; t = tangent point.
History: From electronic version of the journal References: Barnes et al. Paper I. 2011ApJS..196...12B Cat. J/ApJS/196/12 Ma et al. Paper II. 2013ApJ...779...79M Cat. J/ApJ/779/79
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 26-Jan-2017
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