| Description |
Water fountains (WFs) are late AGB and post-AGB objects that show the earliest known manifestation of collimated mass-loss in evolved stars, with jets that have dynamical ages of only 5-100 yr and sizes as small as 100-500 AU. These fast collimated outflows, impinging onto the circumstellar material at the end of the AGB phase, are presumably responsible for the shaping of asymmetric planetary nebulae (PN), with the highly asymmetric H2O-maser-emitting PNe being presumably the immediate descendants of WFs. Therefore, WFs and H2O-PNe are key objects to study the shaping of PNe. Since their thick envelopes make them strongly obscured in the optical and near-IR, their inner circumstellar structure would be best traced at longer wavelengths. Here we propose the acquisition of Herschel PACS and SPIRE deep imaging photometric observations of all known WFs and H2O-PNe to be added to near-IR, mid-IR, submm, and mm data to continue building the spectral energy distribution (SED) of these sources, and to check for the presence of extended material. The characterization and theoretical modeling of their SEDs will be used to infer the presence of disks and to estimate the physical parameters of circumstellar disks and envelopes, which in their turn will impose constraints on the models for the generation of jets in evolved objects. |
