Herschel/PACS far-IR spectral imaging of a jet from an intermediate mass protostar in the OMC-2 region ^⋆,⋆⋆

¹ European Space Astronomy Centre, ESA, PO Box 78, 28691 Villanueva de la Cañada ( Madrid), Spain
e-mail: bgonzale@sciops.esa.int
² ISDEFE, Beatriz de Bobadilla 3, 28040 Madrid, Spain
³ Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, 400005 Mumbai, India
⁴ Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 , USA
⁵ Department of Physics and Astronomy, University of Toledo, 2801 West Bancroft Street, OH 43606, USA
⁶ Max-Planck-Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁷ Instituto de Astrofísica de Andalucía, CSIC, Camino Bajo de Húetor 50, 18008 Granada, Spain
⁸ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁹ NASA Goddard Space Flight Center, MD 8800 Greenbelt, USA
¹⁰ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
¹¹ Naval Research Laboratory, Washington, DC 20375, USA

Received: 13 August 2015
Accepted: 8 August 2016

Abstract

We present the first detection of a jet in the far-IR [O I] lines from an intermediate mass protostar. This jet was detected in a Herschel/PACS spectral mapping study in the [O I] lines of OMC-2 FIR 3 and FIR 4, two of the most luminous protostars in Orion outside of the Orion Nebula. The spatial morphology of the fine structure line emission reveals the presence of an extended photodissociation region (PDR) and a narrow, but intense jet connecting the two protostars. The jet seen in [O I] emission is spatially aligned with the Spitzer/IRAC 4.5 μm jet and the CO (6–5) molecular outflow centered on FIR 3. The mass-loss rate derived from the total [O I] 63 μm line luminosity of the jet is 7.7 × 10^-6M_⊙ yr^-1, more than an order of magnitude higher than that measured for typical low-mass class 0 protostars. The implied accretion luminosity is significantly higher than the observed bolometric luminosity of FIR 4, indicating that the [O I] jet is unlikely to be associated with FIR 4. We argue that the peak line emission seen toward FIR 4 originates in the terminal shock produced by the jet driven by FIR 3. The higher mass-loss rate that we find for FIR 3 is consistent with the idea that intermediate-mass protostars drive more powerful jets than their low-mass counterparts. Our results also call into question the nature of FIR 4.