An APEX survey of outflow and infall toward the youngest protostars in Orion

¹ Center for Astrochemical Studies, Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
² Ritter Astrophysical Research Center, Department of Physics and Astronomy, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA
³ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly Thege Miklós út 15-17, 1121 Budapest, Hungary
e-mail: nagy.zsofia@csfk.mta.hu
⁴ National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22903, USA
⁵ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁶ Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Colaba, Mumbai 400005, India
⁷ European Southern Observatory, 85748 Garching bei München, Germany
⁸ Departmento de Astronomía, Facultad Ciencias Físicas y Matemáticas, Universidad de Concepción, Av. Esteban Iturra s/n Barro Universitario, Casilla 160-C, Concepción, Chile
⁹ Max-Planck-Institut für Astronomie, 69117 Heidelberg, Germany
¹⁰ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

Received: 17 December 2019
Accepted: 23 July 2020

Abstract

Aims. We aim to characterize the outflow properties of a sample of early Class 0 phase low-mass protostars in Orion, which were first identified by the Herschel Space Observatory. We also look for signatures of infall in key molecular lines.

Methods. Maps of CO J = 3–2 and J = 4–3 toward 16 very young Class 0 protostars were obtained using the Atacama Pathfinder EXperiment (APEX) telescope. We searched the data for line wings indicative of outflows and calculated masses, velocities, and dynamical times for the outflows. We used additional HCO⁺, H¹³CO⁺, and NH₃ lines to look for infall signatures toward the protostars.

Results. We estimate the outflow masses, forces, and mass-loss rates based on the CO J = 3–2 and J = 4–3 line intensities for eight sources with detected outflows. We derive upper limits for the outflow masses and forces of sources without clear outflow detections. The total outflow masses for the sources with clear outflow detections are in the range between 0.03 and 0.16 M_⊙ for CO J = 3–2 and between 0.02 and 0.10 M_⊙ for CO J = 4–3. The outflow forces are in the range between 1.57 × 10⁻⁴ and 1.16 × 10⁻³ M_⊙ km s⁻¹ yr⁻¹ for CO J = 3–2 and between 1.14 × 10⁻⁴ and 6.92 × 10⁻⁴ M_⊙ km s⁻¹ yr⁻¹ for CO J = 4–3. Nine protostars in our sample show asymmetric line profiles indicative of infall in HCO⁺, compared to H¹³CO⁺ or NH₃.

Conclusions. The outflow forces of the protostars in our sample show no correlation with the bolometric luminosity, unlike those found by some earlier studies for other Class 0 protostars. The derived outflow forces for the sources with detected outflows are similar to those found for other, more evolved, Class 0 protostars, suggesting that outflows develop quickly in the Class 0 phase.