Water and acetaldehyde in HH212: The first hot corino in Orion

TL;DR

This study reports the first detection of a hot corino in Orion, revealing detailed chemical and physical properties of the inner region of the protostar HH212, and suggesting outflowing gas contributions from a dense disk wind.

Contribution

It provides the first high-resolution images of CH$_3$CHO and HDO in HH212, constrains physical conditions, and links hot corino chemistry with outflow dynamics in Orion.

Findings

First hot corino detection in Orion.

HDO emission shows asymmetric profile indicating outflow contribution.

Dense, warm inner region with specific molecular abundances.

Abstract

Aims: Using the unprecedented combination of high resolution and sensitivity offered by ALMA, we aim to investigate whether and how hot corinos, circumstellar disks, and ejected gas are related in young solar-mass protostars. Methods: We observed CH$_3$CHO and deuterated water (HDO) high-excitation ($E_{\rm u}$ up to 335 K) lines towards the Sun-like protostar HH212--MM1. Results: For the first time, we have obtained images of CH$_3$CHO and HDO emission in the inner $\simeq$ 100 AU of HH212. The multifrequency line analysis allows us to contrain the density ($\geq$ 10$^{7}$ cm$^{-3}$), temperature ($\simeq$ 100 K), and CH$_3$CHO abundance ($\simeq$ 0.2--2 $\times$ 10$^{-9}$) of the emitting region. The HDO profile is asymmetric at low velocities ($\leq$ 2 km s$^{-1}$ from $V_{\rm sys}$). If the HDO line is optically thick, this points to an extremely small ($\sim$ 20--40 AU) and dense ($\ge$ 10$^{9}$ cm$^{-3}$) emitting region. Conclusions: We report the first detection of a hot corino in Orion. The HDO asymmetric profile indicates a contribution of outflowing gas from the compact central region, possibly associated with a dense disk wind.