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Herschel-PACS obser...
Herschel-PACS observations of shocked gas associated with the jets of L1448 and L1157
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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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- Antoniucci, S. (författare)
- Osservatorio Astronomico di Roma
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- Codella, C. (författare)
- Osservatorio Astrofisico di Arcetri,Arcetri Astrophysical Observatory
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- Cabrit, S. (författare)
- LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres, France
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- Giannini, T. (författare)
- Osservatorio Astronomico di Roma
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- Herczeg, G. J. (författare)
- Beijing University of Technology
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- Liseau, René, 1949 (författare)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Tafalla, M. (författare)
- Observatorio Astronómico Nacional (OAN),Spanish National Observatory (OAN)
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- van Dishoeck, E. F. (författare)
- 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)
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(creator_code:org_t)
- 2013-08-20
- 2013
- Engelska.
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 557
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http://publications.... (primary) (free)
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https://www.aanda.or...
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https://research.cha...
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https://doi.org/10.1...
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Abstract
Ämnesord
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- Aims. In the framework of the Water In Star-forming regions with Herschel (WISH) key program, several H2O (E-u > 190 K), high-J CO, [OI], and OH transitions are mapped with Herschel-PACS in two shock positions along two prototypical outflows around the low-luminosity sources L1448 and L1157. Previous Herschel-HIFI H2O observations (E-u = 53-249 K) are also used. The aim is to derive a complete picture of the excitation conditions at the selected shock positions.Methods. We adopted a large velocity gradient analysis (LVG) to derive the physical parameters of the H2O and CO emitting gas. Complementary Spitzer mid-IR H-2 data were used to derive the H2O abundance.Results. Consistent with other studies, at all selected shock spots a close spatial association between H2O, mid-IR H-2, and high-J CO emission is found, whereas the low-J CO emission traces either entrained ambient gas or a remnant of an older shock. The excitation analysis, conducted in detail at the L1448-B2 position, suggests that a two-component model is needed to reproduce the H2O, CO, and mid-IR H-2 lines: an extended warm component (T similar to 450 K) is traced by the H2O emission with E-u = 53-137 K and by the CO lines up to J = 22-21, and a compact hot component (T = 1100 K) is traced by the H2O emission with E-u > 190 K and by the higher-J CO transitions. At L1448-B2 we obtain an H2O abundance (3-4) x 10(-6) for the warm component and (0.3-1.3) x 10(-5) for the hot component and a CO abundance of a few 10-5 in both components. In L1448-B2 we also detect OH and blue-shifted [OI] emission, spatially coincident with the other molecular lines and with [FeII] emission. This suggests a dissociative shock for these species, related to the embedded atomic jet. On the other hand, a non-dissociative shock at the point of impact of the jet on the cloud is responsible for the (HO)-O-2 and CO emission. The other examined shock positions show an H2O excitation similar to L1448-B2, but a slightly higher (HO)-O-2 abundance (a factor of similar to 4).Conclusions. The two gas components may represent a gas stratification in the post-shock region. The extended and low-abundance warm component traces the post-shocked gas that has already cooled down to a few hundred Kelvin, whereas the compact and possibly higher-abundance hot component is associated with the gas that is currently undergoing a shock episode. This hot gas component is more affected by evolutionary effects on the timescales of the outflow propagation, which explains the observed H2O abundance variations.
Ämnesord
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Nyckelord
- stars: formation
- ISM: molecules
- stars: low-mass
- ISM: individual objects: L1157
- ISM: jets and outflows
- ISM: individual objects: L1448
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Santangelo, G.
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Nisini, B.
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Antoniucci, S.
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Codella, C.
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Cabrit, S.
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Giannini, T.
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visa fler...
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Herczeg, G. J.
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Liseau, René, 19 ...
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Tafalla, M.
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van Dishoeck, E. ...
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