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Origin of the hot gas in low-mass protostars: Herschel-PACS spectroscopy of HH 46

van Kempen, T. A. and Blake, G. A. and Lis, D. and Morris, P. (2010) Origin of the hot gas in low-mass protostars: Herschel-PACS spectroscopy of HH 46. Astronomy and Astrophysics, 518 . Art. No. L121. ISSN 0004-6361.

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Aims. “Water In Star-forming regions with Herschel” (WISH) is a Herschel key programme aimed at understanding the physical and chemical structure of young stellar objects (YSOs) with a focus on water and related species. Methods. The low-mass protostar HH 46 was observed with the Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory to measure emission in H_2O, CO, OH, [O _I], and [C_II] lines located between 63 and 186 μm. The excitation and spatial distribution of emission can disentangle the different heating mechanisms of YSOs, with better spatial resolution and sensitivity than previously possible. Results. Far-IR line emission is detected at the position of the protostar and along the outflow axis. The OH emission is concentrated at the central position, CO emission is bright at the central position and along the outflow, and H_2O emission is concentrated in the outflow. In addition, [O_I] emission is seen in low-velocity gas, assumed to be related to the envelope, and is also seen shifted up to 170 km s^(−1) in both the red- and blue-shifted jets. Envelope models are constructed based on previous observational constraints. They indicate that passive heating of a spherical envelope by the protostellar luminosity cannot explain the high-excitation molecular gas detected with PACS, including CO lines with upper levels at >2500 K above the ground state. Instead, warm CO and H_2O emission is probably produced in the walls of an outflow-carved cavity in the envelope, which are heated by UV photons and non-dissociative C-type shocks. The bright OH and [O_I] emission is attributed to J-type shocks in dense gas close to the protostar. In the scenario described here, the combined cooling by far-IR lines within the central spatial pixel is estimated to be 2 × 10^(−2) L_⊙ with 60–80% attributed to J- and C-type shocks produced by interactions between the jet and the envelope.

Item Type:Article
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URLURL TypeDescription Paper
Blake, G. A.0000-0003-0787-1610
Lis, D.0000-0002-0500-4700
Additional Information:© 2010 ESO. Received 31 March 2010, Accepted 10 May 2010, Published Online 16 July 2010. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Table 2 is only available in electronic form at http// This work is made possible thanks to the HIFI guaranteed time programme and the PACS instrument builders. We thank Javier Gracia Carpio, Jeroen Bouwman, Bruno Merín, and Bart VandenBussche for help with the PACS data reduction and many funding agencies for financial support. We also thank the referee for comments that improved this paper.
Subject Keywords:astrochemistry, stars: formation, ISM: molecules, ISM: jets and outflows, ISM: individual objects: HH 46
Record Number:CaltechAUTHORS:20101130-090149064
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Official Citation:Origin of the hot gas in low-mass protostars - Herschel-PACS spectroscopy of HH 46 T. A. van Kempen, L. E. Kristensen, G. J. Herczeg, R. Visser, E. F. van Dishoeck, S. F. Wampfler, S. Bruderer, A. O. Benz, S. D. Doty, C. Brinch, M. R. Hogerheijde, J. K. Jørgensen, M. Tafalla, D. Neufeld, R. Bachiller, A. Baudry, M. Benedettini, E. A. Bergin, P. Bjerkeli, G. A. Blake, S. Bontemps, J. Braine, P. Caselli, J. Cernicharo, C. Codella, F. Daniel, A. M. di Giorgio, C. Dominik, P. Encrenaz, M. Fich, A. Fuente, T. Giannini, J. R. Goicoechea, Th. de Graauw, F. Helmich, F. Herpin, T. Jacq, D. Johnstone, M. J. Kaufman, B. Larsson, D. Lis, R. Liseau, M. Marseille, C. McCoey, G. Melnick, B. Nisini, M. Olberg, B. Parise, J. C. Pearson, R. Plume, C. Risacher, J. Santiago-García, P. Saraceno, R. Shipman, F. van der Tak, F. Wyrowski, U. A. Yıldız, M. Ciechanowicz, L. Dubbeldam, S. Glenz, R. Huisman, R. H. Lin, P. Morris, J. A. Murphy and N. Trappe A&A 518 L121 (2010) DOI: 10.1051/0004-6361/201014615
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21054
Deposited By: Benjamin Perez
Deposited On:30 Nov 2010 17:52
Last Modified:03 Oct 2019 02:19

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