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  • Karska, A.Universiteit Leiden (UL),Leiden University (UL),Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG) (author)

Water in star-forming regions with Herschel (WISH) III. Far-infrared cooling lines in low-mass young stellar objects

  • Article/chapterEnglish2013

Publisher, publication year, extent ...

  • 2013-04-17
  • EDP Sciences,2013
  • electronicrdacarrier

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  • LIBRIS-ID:oai:research.chalmers.se:0450f11f-ad78-4c90-ae7b-4cfa797c0489
  • https://research.chalmers.se/publication/177722URI
  • https://doi.org/10.1051/0004-6361/201220028DOI

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  • Language:English
  • Summary in:English

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  • Subject category:art swepub-publicationtype
  • Subject category:ref swepub-contenttype

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  • Context. Understanding the physical phenomena involved in the earlierst stages of protostellar evolution requires knowledge of the heating and cooling processes that occur in the surroundings of a young stellar object. Spatially resolved information from its constituent gas and dust provides the necessary constraints to distinguish between different theories of accretion energy dissipation into the envelope.Aims. Our aims are to quantify the far-infrared line emission from low-mass protostars and the contribution of different atomic and molecular species to the gas cooling budget, to determine the spatial extent of the emission, and to investigate the underlying excitation conditions. Analysis of the line cooling will help us characterize the evolution of the relevant physical processes as the protostar ages.Methods. Far-infrared Herschel-PACS spectra of 18 low-mass protostars of various luminosities and evolutionary stages are studied in the context of the WISH key program. For most targets, the spectra include many wavelength intervals selected to cover specific CO, H2O, OH, and atomic lines. For four targets the spectra span the entire 55-200 mu m region. The PACS field-of-view covers similar to 47 '' with the resolution of 9.4 ''.Results. Most of the protostars in our sample show strong atomic and molecular far-infrared emission. Water is detected in 17 out of 18 objects (except TMC1A), including 5 Class I sources. The high-excitation H2O 8(18)-7(07) 63.3 mu m line (E-u/k(B) = 1071 K) is detected in 7 sources. CO transitions from J = 14-13 up to J = 49-48 are found and show two distinct temperature components on Boltzmann diagrams with rotational temperatures of similar to 350 K and similar to 700 K. H2O has typical excitation temperatures of similar to 150 K. Emission from both Class 0 and I sources is usually spatially extended along the outflow direction but with a pattern that depends on the species and the transition. In the extended sources, emission is stronger off source and extended on >= 10 000 AU scales; in the compact sample, more than half of the flux originates within 1000 AU of the protostar. The H2O line fluxes correlate strongly with those of the high-J CO lines, both for the full array and for the central position, as well as with the bolometric luminosity and envelope mass. They correlate less strongly with OH fluxes and not with [O I] fluxes. In contrast, [O I] and OH often peak together at the central position.Conclusions. The PACS data probe at least two physical components. The H2O and CO emission very likely arises in non-dissociative (irradiated) shocks along the outflow walls with a range of pre-shock densities. Some OH is also associated with this component, most likely resulting from H2O photodissociation. UV-heated gas contributes only a minor fraction to the CO emission observed by PACS, based on the strong correlation between the shock-dominated CO 24-23 line and the CO 14-13 line. [O I] and some of the OH emission probe dissociative shocks in the inner envelope. The total far-infrared cooling is dominated by H2O and CO, with the fraction contributed by [O I] increasing for Class I sources. Consistent with previous studies, the ratio of total far-infrared line emission over bolometric luminosity decreases with the evolutionary state.

Subject headings and genre

Added entries (persons, corporate bodies, meetings, titles ...)

  • Herczeg, G. J.Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG),Beijing University of Technology (author)
  • van Dishoeck, E. F.Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG),Universiteit Leiden (UL),Leiden University (UL) (author)
  • Wampfler, S. F.Eidgenössische Technische Hochschule Zürich (ETH),Swiss Federal Institute of Technology in Zürich (ETH),Köpenhamns universitet,University of Copenhagen (author)
  • Kristensen, L.Universiteit Leiden (UL),Leiden University (UL) (author)
  • Goicoechea, J. R.Centro de Astrobiologia (CAB) (author)
  • Visser, R.University of Michigan (author)
  • Nisini, B.Osservatorio Astronomico di Roma (author)
  • San Jose-Garcia, I.Universiteit Leiden (UL),Leiden University (UL) (author)
  • Bruderer, S.Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG) (author)
  • Sniady, P.Uniwersytet Wrocławski,University of Wrocław,Polish Academy of Sciences (author)
  • Doty, S.Denison University (author)
  • Fedele, D.Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG) (author)
  • Yildiz, U. A.Universiteit Leiden (UL),Leiden University (UL) (author)
  • Benz, A. O.Eidgenössische Technische Hochschule Zürich (ETH),Swiss Federal Institute of Technology in Zürich (ETH) (author)
  • Bergin, E. A.University of Michigan (author)
  • Caselli, P.Osservatorio Astrofisico di Arcetri,Arcetri Astrophysical Observatory,University of Leeds (author)
  • Herpin, F.Laboratoire d'Astrophysique de Bordeaux,Université de Bordeaux,University of Bordeaux (author)
  • Hogerheijde, M. R.Universiteit Leiden (UL),Leiden University (UL) (author)
  • Johnstone, D.National Research Council Canada,University of Victoria (author)
  • Jorgensen, J. K.Köpenhamns universitet,University of Copenhagen (author)
  • Liseau, René,1949Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)liseau (author)
  • Tafalla, M.Observatorio Astronómico Nacional (OAN),Spanish National Observatory (OAN) (author)
  • van der Tak, F. F. S.Netherlands Institute for Space Research (SRON),Rijksuniversiteit Groningen,University of Groningen (author)
  • Wyrowski, F.Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG) (author)
  • Universiteit Leiden (UL)Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG) (creator_code:org_t)

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  • In:Astronomy and Astrophysics: EDP Sciences5520004-63611432-0746

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