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

¹ INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5x, 50125 Firenze, Italy
e-mail: codella@arcetri.astro.it
² Univ. Grenoble Alpes, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), 38401 Grenoble, France
³ CNRS, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), 38401 Grenoble, France
⁴ LERMA, UMR 8112 du CNRS, Observatoire de Paris, École Normale Supérieure, 61 Av. de l’Observatoire, 75014 Paris, France
⁵ IRAM, 300 rue de la Piscine, 38406 Saint Martin d’Hères, France
⁶ IGN, Observatorio Astronómico Nacional, Alfonso XII 3, 28014 Madrid, Spain
⁷ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

Received: 22 September 2015
Accepted: 18 December 2015

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 CH₃CHO and deuterated water (HDO) high-excitation (E_u up to 335 K) lines towards the Sun-like protostar HH212−MM1.

Results. For the first time, we have obtained images of CH₃CHO and HDO emission in the inner ≃100 AU of HH212. The multifrequency line analysis allows us to contrain the density (≥10⁷ cm^-3), temperature (≃100 K), and CH₃CHO abundance (≃0.2−2 × 10^-9) of the emitting region. The HDO profile is asymmetric at low velocities (≤2 km s^-1 from V_sys). If the HDO line is optically thick, this points to an extremely small (~20−40 AU) and dense (≥10⁹ 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.