Hunting for methanol in a water rich, planet forming disk

Abstract

Methanol (CH3OH), being the simplest possible complex organic molecule (COM), plays a key role among all the chemical species of prebiotic interest detected in space. Across the different stages of Young Stellar Objects (YSOs) evolution, methanol has been found only in a handful of protoplanetary disks. One of the most promising candidate disk to search for methanol is HL Tau, due to the recent discovery of warm water vapour emission (Facchini et al., Nature Astronomy 2024): since methanol and water have a similar volatility, CH3OH is expected to emit from the same region of the disk where water has been detected. In this poster I will present my latest results regarding the analysis of the best ALMA archival datasets to look for methanol inside HL Tau. Employing advanced state-of-art techniques, such as image reconstruction and line stacking in the visibility plane, I was indeed able to derive stringent upper limits on the methanol column density and to discover one possible methanol transition. Within a thermalised framework, I found a low upper limit on the methanol-to-water column density ratio ≲ 10−2 for HL Tauri, similar to the one measured for Solar System comets. This result marks a major step in understanding how the methanol-to-water ratio changes during the evolution of YSOs, especially in the poor-constrained protoplanetary disk stage