Access to Astronomical Catalogues

← Click to display the menu
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 (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:
FileName Lrecl Records Explanations
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/* 0 94 Individual fits spectra
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
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
Note (1): Associations type as follows: HII = HII region IRDC = infrared dark cloud EGO = extended green object
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
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)
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.
Byte-by-byte Description of file: tablea2.dat
Bytes Format Units Label Explanations
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
Acknowledgements: Xindi Tang, xdtang(at)mpifr-bonn.mpg.de
(End) Patricia Vannier [CDS] 19-Oct-2016
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

catalogue service

© UDS/CNRS

Contact