# Deep into the Water Fountains: The case of IRAS 18043-2116

## TL;DR

This study investigates the complex bipolar structures in post-AGB star IRAS 18043-2116 using multi-wavelength observations, revealing jet-driven winds, shock-excited emissions, and potential rotating disks that influence mass-loss processes.

## Contribution

It provides new observational evidence of jet-driven winds and shock-excited emissions in a Water Fountain nebula, highlighting the role of jets and disks in shaping circumstellar structures.

## Key findings

- Detection of radio continuum emission across 1.5-8.0 GHz.
- Identification of high-velocity H₂O maser features and shock-excited H₂ emission.
- Estimated mass-loss rates suggest both jet-driven and ionized outflows.

## 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.