1. Water in star-forming regions with Herschel (WISH) (Corrigendum). V. The physical conditions in low-mass protostellar outflows revealed by multi-transition water observations
- Author
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I. San Jose-Garcia, T. A. van Kempen, Brunella Nisini, M. Tafalla, Joseph C. Mottram, Fabrice Herpin, Lars E. Kristensen, Friedrich Wyrowski, E. F. van Dishoeck, Ruud Visser, Edwin Bergin, Simon Bruderer, Paola Caselli, Arnold O. Benz, René Liseau, G. Santangelo, F. F. S. van der Tak, Doug Johnstone, Michiel R. Hogerheijde, Agata Karska, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Max-Planck-Institut für Extraterrestrische Physik (MPE), foreign laboratories (FL), CERN [Genève], Institute of Astronomy [ETH Zürich], Department of Physics [ETH Zürich] (D-PHYS), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Department of Astronomy [Ann Arbor], University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Natl Res Council Canada, Herzberg Inst Astrophys, Victoria, BC V9E 2E7 Canada, Natl Res Council Canada, Herzberg Inst Astrophys, Victoria, INAF - Osservatorio Astronomico di Roma (OAR), SRON Netherlands Institute for Space Research (SRON), and Max-Planck-Institut für Radioastronomie (MPIFR)
- Subjects
Astrophysics::High Energy Astrophysical Phenomena ,Context (language use) ,Astrophysics ,Astrophysics::Solar and Stellar Astrophysics ,Protostar ,molecules ,ComputingMilieux_MISCELLANEOUS ,Astrophysics::Galaxy Astrophysics ,Line (formation) ,Physics ,Jet (fluid) ,stars: formation ,stars: formation – ISM: jets and outflows – ISM: molecules – stars: protostars – errata ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,Accretion (meteorology) ,stars: protostars ,Star formation ,Astronomy and Astrophysics ,ISM: jets and outflows ,13. Climate action ,Space and Planetary Science ,ISM ,Outflow ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,Low Mass ,addenda ,errata - Abstract
Context. Outflows are an important part of the star formation process as both the result of ongoing active accretion and one of the main sources of mechanical feedback on small scales. Water is the ideal tracer of these effects because it is present in high abundance for the conditions expected in various parts of the protostar, particularly the outflow. Aims. We constrain and quantify the physical conditions probed by water in the outflow-jet system for Class 0 and I sources. Methods. We present velocity-resolved Herschel HIFI spectra of multiple water-transitions observed towards 29 nearby Class 0/ Ip rotostars as part of the WISH guaranteed time key programme. The lines are decomposed into different Gaussian components, with each component related to one of three parts of the protostellar system; quiescent envelope, cavity shock and spot shocks in the jet and at the base of the outflow. We then use non-LTE radex models to constrain the excitation conditions present in the two outflow-related components. Results. Water emission at the source position is optically thick but effectively thin, with line ratios that do not vary with velocity, in contrast to CO. The physical conditions of the cavity and spot shocks are similar, with post-shock H2 densities of order 10 5 −10 8 cm −3 and H2O column densities of order 10 16 −10 18 cm −2 .H 2O emission originates in compact emitting regions: for the spot shocks these correspond to point sources with radii of order 10−200 AU, while for the cavity shocks these come from a thin layer along the outflow cavity wall with thickness of order 1−30 AU. Conclusions. Water emission at the source position traces two distinct kinematic components in the outflow; J shocks at the base of the outflow or in the jet, and C shocks in a thin layer in the cavity wall. The similarity of the physical conditions is in contrast to off-source determinations which show similar densities but lower column densities and larger filling factors. We propose that this is due to the differences in shock properties and geometry between these positions. Class I sources have similar excitation conditions to Class 0 sources, but generally smaller line-widths and emitting region sizes. We suggest that it is the velocity of the wind driving the outflow, rather than the decrease in envelope density or mass, that is the cause of the decrease in H2O intensity between Class 0 and I sources.
- Published
- 2015