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Water emission from...
Water emission from the chemically rich outflow L1157
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- Vasta, M. (författare)
- Osservatorio Astrofisico di Arcetri,Arcetri Astrophysical Observatory
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- Codella, C. (författare)
- Osservatorio Astrofisico di Arcetri,Arcetri Astrophysical Observatory
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- Lorenzani, A. (författare)
- Osservatorio Astrofisico di Arcetri,Arcetri Astrophysical Observatory
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- Santangelo, G. (författare)
- Osservatorio Astronomico di Roma
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- Nisini, B. (författare)
- Osservatorio Astronomico di Roma
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- Giannini, T. (författare)
- Osservatorio Astronomico di Roma
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- Tafalla, M. (författare)
- Observatorio Astronómico Nacional (OAN),Spanish National Observatory (OAN)
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- Liseau, René, 1949 (författare)
- Chalmers tekniska högskola,Chalmers University of Technology
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- van Dishoeck, E. F. (författare)
- 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)
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- Kristensen, L. (författare)
- Universiteit Leiden (UL),Leiden University (UL)
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(creator_code:org_t)
- 2012-01-16
- 2012
- Engelska.
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 537, s. Article Number: A98 -
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- Context. In the framework of the Herschel-WISH key program, several ortho-H2O and para-H2O emission lines, in the frequency range from 500 to 1700 GHz, were observed with the HIFI instrument in two bow-shock regions (B2 and R) of the L1157 cloud, which hosts what is considered to be the prototypical chemically-rich outflow. Aims. Our primary aim is to analyse water emission lines as a diagnostic of the physical conditions in the blue (B2) and red-shifted (R) lobes to compare the excitation conditions. Methods. For this purpose, we ran the non-LTE RADEX model for a plane-parallel geometry to constrain the physical parameters (T-kin, N-H2O and nH(2)) of the water emission lines detected. Results. A total of 5 ortho- and para-(H2O)-O-16 plus one o-(H2O)-O-18 transitions were observed in B2 and R with a wide range of excitation energies (27K = 300 K). The presence of the broad red-shifted wings and multiple peaks in the spectra of the R region, prompted the modelling of two components. High velocities are associated with relatively low temperatures (similar to 100 K), N-H2O similar or equal to 5 x 10(12)-5 x 10(13) cm(-2) and densities nH(2) similar or equal to 10(6)-10(8) cm(-3). Lower velocities are associated with higher excitation conditions with T-kin >= 300 K, very dense gas (nH(2) similar to 10(8) cm(-3)) and low column density (N-H2O = 15 '') region, whilst we cannot rule out the possibility that the emission in R arises from a smaller (>3 '') region. In this context, H2O seems to be important in tracing different gas components with respect to other molecules, e.g. such as SiO, a classical jet tracer. We compare a grid of C-and J-type shocks spanning different velocities (10 to 40 km s(-1)) and two pre-shock densities (2 x 10(4) and 2 x 10(5) cm(-3)), with the observed intensities. Although none of these models seem to be able to reproduce the absolute intensities of the water emissions observed, it appears that the occurrence of J-shocks, which can compress the gas to very high densities, cannot be ruled out in these environments.
Ämnesord
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Nyckelord
- sio
- magnetohydrodynamic shock-waves
- h-2
- excitation
- ISM: molecules
- program
- clouds
- ammonia
- chess spectral
- molecular outflow
- stars: formation
- star-forming regions
- ISM: jets and outflows
- stars
- low-mass
- survey
- stars: individual: L1157
Publikations- och innehållstyp
- art (ämneskategori)
- ref (ämneskategori)
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Till lärosätets databas
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Vasta, M.
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Codella, C.
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Lorenzani, A.
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Santangelo, G.
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Nisini, B.
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Giannini, T.
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visa fler...
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Tafalla, M.
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Liseau, René, 19 ...
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van Dishoeck, E. ...
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Kristensen, L.
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