Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 1K046

The CHESS survey of the L1157-B1 bow-shock: Dissecting the water content

Busquet, Gemma (INAF-Istituto di Astrofisica e Planetologia Spaziali)
Lefloch, Bertrand (CNRS-INSU, Insitut de Planétologie et d\'Astrophysique de Grenoble (IPAG))
Benedettini, Milena (INAF-Istituto di Astrofisica e Planetologia Spaziali)
Ceccarelli, Cecilia (CNRS-INSU, Insitut de Planétologie et d\'Astrophysique de Grenoble (IPAG))
Codella, Claudio (INAF-Osservatorio Astrofisico di Arcetri)
Cabrit, Sylvie (Observatoire de Paris, LERMA)
Nisini, Brunella (INAF-Osservatorio Astronomico di Roma)
Viti, Serena (Department of Physics and Astronomy, University College London)
Gómez-Ruiz, Arturo (INAF-Osservatorio Astrofisico di Arcetri)
Gusdorf, Antoine ( LERMA, Observatoire de Paris, École Normale Supérieure)
Di Giorgio, Anna Maria (INAF-Istituto di Astrofisica e Planetologia Spaziali)
Wiesenfeld, Laurent (CNRS-INSU, Insitut de Planétologie et d\'Astrophysique de Grenoble (IPAG))

Molecular outflows powered by young protostars strongly affect the kinematics and chemistry of the natal molecular cloud through strong shocks, resulting in an increase of the abundance of several species. In particular, water is a powerful tracer of shocked material due to its sensitivity to both physical conditions and chemical processes. The observations of the “Chemical Herschel Survey of Star forming regions” (CHESS) key program towards the shock region L1157-B1 offered a unique and comprehensive view of the water emission in a typical protostellar bow shock across the submillimeter and far-infrared window. A grand total of 13 water lines have been detected with the PACS and HIFI instruments, probing a wide range of excitation conditions and providing us with a detailed picture on both the kinematics and the spatial distribution of water emission. Several gas components have been identified coexisting in the L1157-B1 shock region. Large Velocity Gradient (LVG) analysis reveals that these components have different excitation conditions: i) a warm (T~250 K) and dense (n(H2)~10^6 cm-3) gas component seen also with the CO lines and associated with the partly dissociative shock produced by the impact of the protostellar jet against the bow shock; ii) a compact (size~5’’), hot (T~700 K), and less dense (n(H2)~10^4 cm-3) gas component, and iii) an extended component associated with the B1 outflow cavity. These three components present clear differences in terms of water enrichment. Finally, we confront the physical and chemical properties of the H2O emission to the predictions of current shock models.

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