We report on recent results from our successful and pioneering observational program with ALMA to study emerging ultracom pact HII regions of pre-Planetary Nebulae (pPNe) using mm-wavelength recombination lines (mRRLs) as new optimal tracers. We focus on our study of two poster-child pPNe, namely, M2-9 and CRL618. We reveal the structure and kinematics of the en igmatic inner nebular regions of these objects with an unprecedented angular resolution down to 20-30mas (~15-30AU). For both targets, the ionized central regions are elongated along the main symmetry axis of the large-scale nebulae, consiste nt with bipolar winds, and show notable axial velocity gradients with expansion velocities of up to ~100km/s. The H30a pr ofiles exhibit time variability, reflecting changes in the physical properties and kinematics on scales of a few years. O ur ongoing analysis employs 3D, non-LTE radiative transfer modeling, providing a detailed description of the innermost la yers of these well known pPNe with exceptional clarity.
@article{arxiv.2312.04188,
title = {Zooming on the emerging ionized regions of pPNe with ALMA},
author = {C. Sánchez Contreras and D. Tafoya and J. P. Fonfría and J. Alcolea and A. Castro-Carrizo and V. Bujarrabal},
journal= {arXiv preprint arXiv:2312.04188},
year = {2025}
}
Comments
6 pages, 3 figures. Proceedings IAU Symposium no. 384