Revisiting the shocks in BHR71: new observational constraints and H2O predictions for Herschel

Abstract

During the formation of a star, material is ejected along powerful jets that impact the ambient material. This outflow phenomenon plays an important role in the regulation of star formation. Understanding the associated shocks and their energetic effects is therefore essential to the study of star formation. We present comparisons of shock models with observations of H${}_2$ and SiO emission in the bipolar outflow BHR71, and predict water emission, under the basic assumption that the emission regions of the considered species coincide, at the resolution of currently available observations. New SiO observations from APEX are presented, and combined with \textit{Spitzer} and ground-based observations of H${}_2$ to constrain shock models. The shock regions associated with targeted positions in the molecular outflow are studied by means of a 1D code that generates models of the propagation of stationary shock waves, and approximations to non-stationary ones. The SiO emission in the inner part of the outflow is concentrated near the apex of the corresponding bow-shock that is also seen in the pure rotational transitions of H${}_2$. Simultaneous modelling is possible for H${}_2$ and SiO and leads to constraints on the silicon pre-shock distribution on the grain mantles and/or cores. The best-fitting models are found to be of the non-stationary type, but the degeneracy of the solutions is still large. Pre-shock densities of 10${}^4$ and 10${}^5$ cm${}^{-3}$ are investigated, and the associated best-model candidates have rather low velocity (respectively, 20-30 and 10-15 km s${}^{-1}$) and are not older than 1000 years. We provide emission predictions for water, focusing on the brightest transitions, to be observed with the PACS and HIFI instruments of the \textit{Herschel} Telescope.

22 pages (12 text + 10 appendix), 8 figures, 8 tables (4 text + 4 appendix). Abstract has been amended to fullfill arxiv requirements

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• SiO line emission from C-type shock waves : interstellar jets and outflows
• Quasi-classical rate coefficient calculations for the rotational (de)excitation of H2O by H2
• Molecular oxygen in the rho Ophiuchi cloud
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• APECS - The Atacama Pathfinder Experiment Control System
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Cited by in corpus (19)

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• The Herschel HIFI water line survey in the low-mass proto-stellar outflow L1448
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• Shock excitation of H${}_2$ in the James Webb Space Telescope era
• Constraining the Infalling Envelope Models of Embedded Protostars: BHR 71 and its Hot Corino
• Evidence of a SiO collimated outflow from a massive YSO in IRAS 17233-3606
• JWST Observations of Young protoStars (JOYS). Overview of gaseous molecular emission and absorption in low-mass protostars
• The Class 0 Protostar BHR71: Herschel Observations and Dust Continuum Models
• APEX observations of supernova remnants - I. Non-stationary MHD-shocks in W44
• Impacts of pure shocks in the BHR71 bipolar outflow
• The water abundance behind interstellar shocks: results from $Herschel$/PACS and $Spitzer$/IRS observations of H${}_2$O, CO, and H${}_2$
• Water emission from the high-mass star-forming region IRAS 17233-3606. High water abundances at high velocities
• H${}_2$ emission from non-stationary magnetized bow shocks
• The shocked gas of the BHR71 outflow observed by Herschel: indirect evidence for an atomic jet
• Early Planet Formation in Embedded Disks (eDisk). XI. A high-resolution view toward the BHR 71 Class 0 protostellar wide binary
• Challenging shock models with SOFIA OH observations in the high-mass star-forming region Cepheus A
• Molecular Line Emission from Multifluid Shock Waves. I. Numerical Methods and Benchmark Tests