J/A+A/629/A8 IRAS 16342-3814 12CO (1-0) and (3-2) datacubes (Tafoya+, 2019)
Spatio-kinematical model of the collimated molecular outflow in the
water-fountain nebula IRAS 16342-3814.
Tafoya D., Orosz G., Vlemmings W.H.T., Sahai R., Perez-Sanchez A.F.
<Astron. Astrophys. 629, A8 (2019)>
=2019A&A...629A...8T 2019A&A...629A...8T (SIMBAD/NED BibCode)
ADC_Keywords: Infrared sources ; Carbon monoxide
Keywords: stars: AGB and post-AGB - stars: jets - stars: mass-loss -
stars: winds, outflows - submillimeter: star
Abstract:
Water-fountain nebulae are asymptotic giant branch (AGB) and post-AGB
objects that exhibit high-velocity outflows traced by water-maser
emission. Their study is important for understanding the interaction
between collimated jets and the circumstellar material that leads to
the formation of bipolar and/or multi-polar morphologies in evolved
stars.
The aim of this paper is to describe the three-dimensional morphology
and kinematics of the molecular gas of the water-fountain nebula IRAS
16342-3814.
Data was retrieved from the ALMA archive for analysis using a simple
spatio-kinematical model. The software SHAPE was employed to construct
a three-dimensional, spatio-kinematical model of the molecular gas in
IRAS 16342-3814, and to then reproduce the intensity distribution
and position-velocity diagram of the CO emission from the ALMA
observations to derive the morphology and velocity field of the gas.
Data from CO(J=1->0) supported the physical interpretation of the
model.
A spatio-kinematical model that includes a high-velocity collimated
outflow embedded within material expanding at relatively lower
velocity reproduces the images and position-velocity diagrams from the
observations. The derived morphology is in good agreement with
previous results from IR and water-maser emission observations. The
high-velocity collimated outflow exhibits deceleration across its
length, while the velocity of the surrounding component increases with
distance. The morphology of the emitting region, the velocity field,
and the mass of the gas as function of velocity are in excellent
agreement with the properties predicted for a molecular outflow driven
by a jet. The timescale of the molecular outflow is estimated to be
∼70-100yr. The scalar momentum carried by the outflow is much larger
than it can be provided by the radiation of the central star. An
oscillating pattern was found associated with the high-velocity
collimated outflow. The oscillation period of the pattern is
T~=60-90yr and its opening angle is θop~=2°.
The CO (J=3->2) emission in IRAS 16342-3814 is interpreted in terms
of a jet-driven molecular outflow expanding along an elongated region.
The position-velocity diagram and the mass spectrum reveal a feature
due to entrained material that is associated with the driving jet.
This feature is not seen in other more evolved objects that exhibit
more developed bipolar morphologies. It is likely that the jet in
those objects has already disappeared since it is expected to last
only for a couple hundred years. This strengthens the idea that water
fountain nebulae are undergoing a very short transition during which
they develop the collimated outflows that shape the circumstellar
envelopes. The oscillating pattern seen in the CO high-velocity
outflow is interpreted as due to precession with a relatively small
opening angle. The precession period is compatible with the period of
the corkscrew pattern seen at IR wavelengths. We propose that the
high-velocity molecular outflow traces the underlying primary jet that
produces such a pattern.
Description:
Two fits files containing the data that corresponds to the images
shown in Figs. 2 and 7.
Objects:
------------------------------------------------------------------------
RA (2000) DE Designation(s)
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16 37 39.87 -38 20 17.4 IRAS 16342-3814 = NAME Water Fountain Nebula
------------------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 161 2 List of fits datacubes
fits/* . 2 Individual fits datacubes
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 31 I4 --- Nz Number of slices
33- 55 A23 "datime" Obs.date Observation date
57- 63 F7.3 GHz bFREQ Lower value of frequency interval
65- 71 F7.3 GHz BFREQ Upper value of frequency interval
73- 78 I6 Hz dFREQ Frequency resolution
80- 86 I7 Kibyte size Size of FITS file
88-121 A34 --- FileName Name of FITS file, in subdirectory fits
123-161 A39 --- Title Title of the FITS file
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Acknowledgements:
Daniel Tafoya, danli.tafoya(at)gmail.com
(End) Patricia Vannier [CDS] 13-Aug-2019