J/A+A/638/A105 8 massive proto-cluster clumps NH2D & NH3 cubes (Zhang+, 2020)
Probing the initial conditions of high-mass star formation.
IV. Gas dynamics and NH2D chemistry in high-mass pre/protocluster clumps.
Zhang C.-P., Li G.-X., Pillai T., Csengeri T., Wyrowski F., Menten K.M.,
Pestalozzi M.R.
<Astron. Astrophys. 638, A105 (2020)>
=2020A&A...638A.105Z 2020A&A...638A.105Z (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Interferometry ; Radio sources ;
Millimetric/submm sources
Keywords: stars formation - techniques interferometer - ISM clouds -
methods: observational
Abstract:
The initial stage of star formation is very difficult to study because
of its high density (nH2> 106cm-3) and low temperature
(Tdust<18K). Under such conditions, many molecules become depleted
from the gas phase by freezing out onto dust grains. However, the
deuterated species could remain gaseous under these extreme conditions
and are thus ideal tracers.
We investigate the gas dynamics and NH2D chemistry in eight massive
pre/protocluster clumps (G18.17, G18.21, G23.97N, G23.98, G23.44,
G23.97S, G25.38, and G25.71). We present NH2D 111-101 (at
85.926GHz), NH3 (1,1) and (2,2) observations in the eight clumps
using the PdBI and the VLA, respectively. We use 3D GAUSSCLUMPS to
extract NH2D cores and provide a statistical view of their deuterium
chemistry. We use NH3 (1,1) and (2,2) data to investigate the
temperature and dynamics of dense and cold objects.
We find that the distribution between deuterium fractionation and
kinetic temperature shows a number density peak at around
Tkin=16.1K, and the NH2D cores are mainly located at a temperature
range of 13.0 to 22.0K. The 3.5mm continuum cores have a kinetic
temperature with the median width of 22.1±4.3K, which is obviously
higher than the temperature in NH2D cores. We detect seven extremely
high deuterium fractionation of 1.0≤Dfrac≤1.41. We find that the
NH2D emission does not appear to coincide exactly with either dust
continuum or NH3 peak positions, but often surrounds the
star-formation active regions. This suggests that the NH2D has been
destroyed by the central young stellar object (YSO) due to its
heating. The detected NH2D lines are very narrow with a median width
of 0.98±0.02km/s, which is dominated by non-thermal broadening. The
extracted NH2D cores are gravitationally bound (αvir<1), are
likely prestellar or starless, and can potentially form
intermediate-mass or high-mass stars in future. Using NH3 (1,1) as a
dynamical tracer, we find very complicated dynamical movement in all
the eight clumps, which can be explained by a combined process with
outflow, rotation, convergent flow, collision, large velocity
gradient, and rotating toroids.
High deuterium fractionation strongly depends on the temperature
condition. NH2D is a poor evolutionary indicator of high-mass star
formation in evolved stages, but a useful tracer in the starless and
prestellar cores.
Description:
We present NH2D 111-101 (at 85.926GHz), NH3 (1,1) and (2,2)
observations in the eight clumps (G18.17, G18.21, G23.97N, G23.98,
G23.44, G23.97S, G25.38, and G25.71) using the PdBI and the VLA,
respectively. We use 3D GAUSSCLUMPS to extract NH2D cores and
provide a statistical view of their deuterium chemistry. We use NH3
(1,1) and (2,2) data to investigate the temperature and dynamics of
dense and cold objects. We find that high deuterium fractionation
strongly depends on the temperature condition, and NH2D is a poor
evolutionary indicator of high-mass star formation in evolved stages,
but a useful tracer in the starless and prestellar cores.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
sources.dat 50 8 *List of studied sources
list.dat 142 24 List of fits datacubes
fits/* . 24 Individual fits datacubes
--------------------------------------------------------------------------------
Note on sources.dat: Parameters from Paper III, Zhang et al., 2019,
Cat. J/A+A/627/A85.
--------------------------------------------------------------------------------
See also:
J/A+A/530/A118 : G29.96-0.02 and G35.20-1.74 1mm and 3mm maps (Pillai+, 2011)
J/A+A/627/A85 : 8 massive proto-cluster clumps observations (Zhang+, 2019)
Byte-by-byte Description of file: sources.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Source name
9- 24 A16 --- ATLASGAL ATLASGAL name (GLLL.llll+B.bbbb)
26- 27 I2 h RAh Phase center right ascension (J2000)
29- 30 I2 min RAm Phase center right ascension (J2000)
32- 37 F6.3 s RAs Phase center right ascension (J2000)
39 A1 --- DE- Phase center declination sign (J2000)
40- 41 I2 deg DEd Phase center declination (J2000)
43- 44 I2 arcmin DEm Phase center declination (J2000)
46- 50 F5.2 arcsec DEs Phase center declination (J2000)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Source name
9- 17 F9.5 deg RAdeg Right Ascension of center (J2000)
18- 26 F9.5 deg DEdeg Declination of center (J2000)
28- 30 I3 --- Nx Number of pixels along X-axis
32- 34 I3 --- Ny Number of pixels along Y-axis
36- 38 I3 --- Nz Number of pixels along Z-axis
40- 60 A21 "datime" Obs.Date Observation date
62- 69 F8.2 m/s bVRAD Lower value of VRAD interval
71- 78 F8.1 m/s BVRAD Upper value of VRAD interval
80- 86 F7.3 m/s dVRAD VRAD resolution
88- 93 I6 Kibyte size Size of FITS file
95-112 A18 --- FileName Name of FITS file, in subdirectory fits
114-142 A29 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Chuan-Peng Zhang, zcp0507(at)gmail.com
References:
Pillai et al., Paper I 2007A&A...467..207P 2007A&A...467..207P
Pillai et al., Paper II 2011A&A...530A.118P 2011A&A...530A.118P, Cat. J/A+A/530/A118
Zhang et al., Paper III 2019A&A...627A..85Z 2019A&A...627A..85Z, Cat. J/A+A/627/A85
(End) Chuan-Peng Zhang [NAOC, Beijing], Patricia Vannier [CDS] 04-May-2020