Research Note

Disentangling the jet emission from protostellar systems

The ALMA view of VLA1623^⋆

¹ Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monteporzio Catone, Italy
e-mail: gina.santangelo@oa-roma.inaf.it
² Max-Planck Institut für Extraterrestrische Physik (MPE), Giessenbachstr.1, 85748 Garching, Germany
³ Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Florence, Italy
⁴ Institute of Astronomy and Department of Physics, National Tsing Hua University, 101 Section 2 Kuang Fu Road, 30013 Hsinchu, Taiwan
⁵ Academia Sinica Institute of Astronomy and Astrophysics, PO Box 23-141, 10617 Taipei, Taiwan
⁶ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

Received: 28 April 2015
Accepted: 5 June 2015

Abstract

Context. High-resolution studies of class 0 protostars represent the key to constraining protostar formation models. VLA16234−2417 represents the prototype of class 0 protostars, and it has been recently identified as a triple non-coeval system.

Aims. We aim at deriving the physical properties of the jets in VLA16234−2417 using tracers of shocked gas.

Methods. ALMA Cycle 0 Early Science observations of CO(2−1) in the extended configuration are presented in comparison with previous SMA CO(3−2) and Herschel-PACS [Oi] 63 μm observations. Gas morphology and kinematics were analysed to constrain the physical structure and origin of the protostellar outflows.

Results. We reveal a collimated jet component associated with the [Oi] 63 μm emission at about 8′′ (~960 AU) from source B. This newly detected jet component is inversely oriented with respect to the large-scale outflow driven by source A, and it is aligned with compact and fast jet emission very close to source B (about 0''̣3) rather than with the direction perpendicular to the A disk. We also detect a cavity-like structure at low projected velocities, which surrounds the [Oi] 63 μm emission and is possibly associated with the outflow driven by source A. Finally, no compact outflow emission is associated with source W.

Conclusions. Our high-resolution ALMA observations seem to suggest there is a fast and collimated jet component associated with source B. This scenario would confirm that source B is younger than A, that it is in a very early stage of evolution, and that it drives a faster, more collimated, and more compact jet with respect to the large-scale slower outflow driven by A. However, a different scenario of a precessing jet driven by A cannot be firmly excluded from the present observations.