J/A+A/598/A30 Massive star forming molecular clumps Tkin (Tang+, 2017)
Kinetic temperature of massive star forming molecular clumps measured with
formaldehyde.
Tang X.D., Henkel C., Menten K.M., Zheng X.W., Esimbek J., Zhou J.J.,
Yeh C.C., Konig C., Yuan Y., He Y.X., Li D.L.
<Astron. Astrophys. 598, A30 (2017)>
=2017A&A...598A..30T 2017A&A...598A..30T (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Spectroscopy ; Radio lines
Keywords: stars: formation - stars: massive - ISM: clouds - ISM: molecules -
radio lines: ISM
Abstract:
For a general understanding of the physics involved in the star
formation process, measurements of physical parameters such as
temperature and density are indispensable. The chemical and physical
properties of dense clumps of molecular clouds are strongly affected
by the kinetic temperature. Therefore, this parameter is essential for
a better understanding of the interstellar medium. Formaldehyde, a
molecule which traces the entire dense molecular gas, appears to be
the most reliable tracer to directly measure the gas kinetic
temperature.We aim to determine the kinetic temperature with spectral
lines from formaldehyde and to compare the results with those obtained
from ammonia lines for a large number of massive clumps.Three 218 GHz
transitions (JKAKC=303-202, 322-221, and 321-220) of
para-H2CO were observed with the 15m James Clerk Maxwell Telescope
(JCMT) toward 30 massive clumps of the Galactic disk at various stages
of high-mass star formation. Using the RADEX non-LTE model, we derive
the gas kinetic temperature modeling the measured para-H2CO
322-221/303-202 and 321-220/303-202 ratios. The gas
kinetic temperatures derived from the para-H2CO
(321-220/303-202) line ratios range from 30 to 61K with an
average of 46K. A comparison of kinetic temperature derived from
para-H2CO, NH3, and the dust emission indicates that in many cases
para-H2CO traces a similar kinetic temperature to the NH3
(2,2)/(1,1) transitions and the dust associated with the HII regions.
Distinctly higher temperatures are probed by para-H2CO in the clumps
associated with outflows/shocks. Kinetic temperatures obtained from
para-H2CO trace turbulence to a higher degree than NH3 (2,2)/(1,1)
in the massive clumps. The non-thermal velocity dispersions of
para-H2CO lines are positively correlated with the gas kinetic
temperature. The massive clumps are significantly influenced by
supersonic non-thermal motions.
Description:
We have selected 30 massive clumps of the Galactic disk at various
stages of high-mass star formation and with strong NH3 emission from
the ATLASGAL survey (see Table 1).
Our observations were carried out in 2015 April, July, and October
with the 15m James Clerk Maxwell Telescope telescope (JCMT) on Mauna
Kea.
The beam size is ∼23" and the main-beam efficiency is
ηmb=Ta*/Tmb~=0.7 at 218GHz. The para-H2CO JKAKC
=303-202, 322-221, and 321-220 transitions have rest
frequencies of 218.222, 218.475, and 218.760GHz, respectively, which
are measured simultaneously by employing the ACSIS digital
autocorrelation spectrometer with the special backend configuration
RxAH2CO250x3 allowing for three windows, each with a bandwidth of
250MHz. This provides a velocity resolution of 0.084km/s for
para-H2CO (303-202 and 322-221) and 0.042km/s for
para-H2CO (321-220); CH3OH (422-312) at 218.440GHz is also
observed together with para-H2CO (322-221).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 200 30 Source parameters
table2.dat 48 18 CH3OH(422-312) spectral parameters
table3.dat 38 25 Para-H2CO column densities and kinetic
temperature
table5.dat 53 30 Thermal and non-thermal parameters
tablea2.dat 63 76 Para-H2CO spectral parameters
sp/* . 94 Individual fits spectra
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Source name (GLL.ll+B.bb)
13- 14 I2 h RAh Right ascension (J2000)
16- 17 I2 min RAm Right ascension (J2000)
19- 23 F5.2 s RAs Right ascension (J2000)
25 A1 --- DE- Declination sign (J2000)
26- 27 I2 deg DEd Declination (J2000)
29- 30 I2 arcmin DEm Declination (J2000)
32- 36 F5.2 arcsec DEs Declination (J2000)
38- 41 F4.2 10+15cm-2 N(NH3) NH3 column density
43- 47 F5.2 10+22cm-2 N(NH2) ?=- NH2 column density
49- 53 F5.2 Jy S870um Flux density at 870um
55- 58 F4.1 K TkinNH3 Kinetic temperature from NH3
60- 63 F4.1 K e_TkinNH3 rms uncertainty on TkinNH3
65- 68 F4.1 K Tdust ?=- Kinematic temperature from dust(HiGal)
70- 73 F4.1 K e_Tdust ? rms uncertainty on Tdust
75- 79 F5.2 kpc Dist Distance
81- 90 A10 --- Assoc Association (1)
92-113 A22 --- Sp1 Fits filename of CH3OH spectra
in sp subdirectory
115-142 A28 --- Sp2 Fits filename of H2CO 303-202 spectra
in sp subdirectory
144-171 A28 --- Sp3 Fits filename of H2CO 321-220 spectra
in sp subdirectory
173-200 A28 --- Sp4 Fits filename of H2CO 322-221 spectra
in sp subdirectory
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Note (1): Associations type as follows:
HII = HII region
IRDC = infrared dark cloud
EGO = extended green object
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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- 11 A11 --- Name Source name (GLL.ll+B.bb)
13- 16 F4.2 K.km/s ITmbdv ?=- Integrated intensity
18- 21 F4.2 K.km/s e_ITmbdv ? rms uncertainty on ITmbdv
23- 28 F6.2 km/s Vlsr LSR velocity
30- 33 F4.2 km/s e_Vlsr rms uncertainty on Vlsr
35- 38 F4.2 km/s FWHM ?=- FWHM
40- 43 F4.2 km/s e_FWHM ? rms uncertainty on FWHM
45- 48 F4.2 K Tmb ?=- Main beam brightness temperature
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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- 11 A11 --- Name Source name (GLL.ll+B.bb)
13- 19 E7.2 cm-2 N(para-H2CO) para-H2CO column density for
n(H2)-105cm-3
21- 22 I2 K Tkin1 ?=- Kinetic temperature derived by
para-H2CO (322-221/303-202)
24 I1 K E_Tkin1 ?=- Error on Tkin1 (upper value)
26 I1 K e_Tkin1 ?=- Error on Tkin1 (lower value)
28- 29 I2 K Tkin2 ?=- Kinetic temperature derived by
para-H2CO (321-220/303-202)
31- 32 I2 K E_Tkin2 ?=- Error on Tkin2 (upper value)
34- 35 I2 K e_Tkin2 ?=- Error on Tkin2 (lower value)
37- 38 I2 K Tlte ? =- LTE kinetic temperature
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Source name (GLL.ll+B.bb)
13- 16 F4.2 km/s sigmaT1 NH3 thermal line width
18- 21 F4.2 km/s sigmaNT1 NH3 non-thermal velocity dispersion
23- 26 F4.2 km/s as1 NH3 thermal sound speed
28- 32 F5.3 --- Rp1 NH3 ratio of thermal to nonthermal
pressure (1)
34- 37 F4.2 km/s sigmaT2 ?=- H2CO thermal line width
39- 42 F4.2 km/s sigmaNT2 ?=- H2CO non-thermal velocity dispersion
44- 47 F4.2 km/s as2 ?=- H2CO thermal sound speed
49- 53 F5.3 --- Rp2 ?=- H2CO ratio of thermal to nonthermal
pressure (2)
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Note (1): ratio obtained from NH3 (1,1) with kinetic temperatures derived from
the NH3 (2,2)/(1,1) line intensity ratio.
Note (2): ratio obtained from para-H2CO (303-202) with kinetic
temperatures derived from para-H2CO (321-220/303-202) line
intensity ratio.
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Source name (GLL.ll+B.bb)
13- 25 A13 --- Trans Transition
27- 31 F5.2 K.km/s iTmbdV ?=- Integrated intensity
33- 36 F4.2 K.km/s e_iTmbdV ? rms uncertainty on iTmbdV
38- 43 F6.2 km/s Vlsr ?=- LSR velocity
45- 48 F4.2 km/s e_Vlsr ? rms uncertainty on Vlsr
50- 53 F4.2 km/s FWHM ?=- FWHM
55- 58 F4.2 km/s e_FWHM ? rms uncertainty on FWHM
60- 63 F4.2 K Tmb ?=- Main beam brightness temperature
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Acknowledgements:
Xindi Tang, xdtang(at)mpifr-bonn.mpg.de
(End) Patricia Vannier [CDS] 19-Oct-2016