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 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:
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FileName Lrecl Records Explanations
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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
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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
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Bytes Format Units Label Explanations
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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- 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- 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 [12]? Uncertainty in amaj
88- 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
100-100 I1 deg e_PA ? Uncertainty in PA
102-102 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
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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.
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Byte-by-byte Description of file: table[23].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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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- 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
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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.
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History:
From electronic version of the journal
References:
Barnes et al. Paper I. 2011ApJS..196...12B 2011ApJS..196...12B Cat. J/ApJS/196/12
Ma et al. Paper II. 2013ApJ...779...79M 2013ApJ...779...79M Cat. J/ApJ/779/79
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 26-Jan-2017