Title: Deep into the Water Fountains: The case of IRAS 18043-2116,
Abstract: (Abridged) The formation of large-scale (hundreds to few thousands of AU)
bipolar structures in the circumstellar envelopes (CSEs) of post-Asymptotic
Giant Branch (post-AGB) stars is poorly understood. The shape of these
structures, traced by emission from fast molecular outflows, suggests that the
dynamics at the innermost regions of these CSEs does not depend only on the
energy of the radiation field of the central star. Deep into the Water
Fountains is an observational project based on the results of programs carried
out with three telescope facilities: The Karl G. Jansky Very Large Array
(JVLA), The Australia Telescope Compact Array (ATCA), and the Very Large
Telescope (SINFONI-VLT). Here we report the results of the observations towards
the WF nebula IRAS 18043$-$2116: Detection of radio continuum emission in the
frequency range 1.5GHz - 8.0GHz; H$_{2}$O maser spectral features and radio
continuum emission detected at 22GHz, and H$_{2}$ ro-vibrational emission lines
detected at the near infrared. The high-velocity H$_{2}$O maser spectral
features, and the shock-excited H$_{2}$ emission detected could be produced in
molecular layers which are swept up as a consequence of the propagation of a
jet-driven wind. Using the derived H$_{2}$ column density, we estimated a
molecular mass-loss rate of the order of $10^{-9}$M$_{\odot}$yr$^{-1}$. On the
other hand, if the radio continuum flux detected is generated as a consequence
of the propagation of a thermal radio jet, the mass-loss rate associated to the
outflowing ionized material is of the order of 10$^{-5}$M$_{\odot}$yr$^{-1}$.
The presence of a rotating disk could be a plausible explanation for the
mass-loss rates estimated.