Water in low-mass star-forming regions with Herschel: HIFI spectroscopy of NGC1333

L. E. Kristensen , R. Visser , E. F. van Dishoeck , U. A. Yildiz , S. D. Doty , G. J. Herczeg , F. -C. Liu , B. Parise (1) , J. K. Jørgensen , T. A. van Kempen , C. Brinch , S. F. Wampfler , S. Bruderer , A. O. Benz , M. R. Hogerheijde , E. Deul , R. Bachiller (2) , Alain Baudry (3, 4, 5, 6) , M. Benedettini (2) , E. A. Bergin (7) , P. Bjerkeli , G. A. Blake (8) , Sylvain Bontemps (3, 4, 5, 6) , J. Braine (3, 4, 5, 6) , P. Caselli (9) , J. Cernicharo (10) , C. Codella (2) , F. Daniel , Th. de Graauw , A. M. Di Giorgio , C. Dominik (11) , P. Encrenaz (12) , M. Fich , A. Fuente (2) , T. Giannini , J. R. Goicoechea (12) , F. Helmich (2) , Fabrice Herpin (3, 4, 5, 6) , T. Jacq (3, 4, 5, 6) , D. Johnstone , M. J. Kaufman , B. Larsson (2) , D. Lis (2) , R. Liseau , M. Marseille (3, 4, 5, 6, 13) , C. Mccoey , G. Melnick (2) , D. Neufeld (2) , B. Nisini (14) , M. Olberg (15) , J. C. Pearson , R. Plume , C. Risacher (16) , J. Santiago-Garcia , P. Saraceno (17) , R. Shipman , M. Tafalla , A. G. G. M. Tielens (13) , F. van Der Tak (2) , F. Wyrowski (18) , D. Beintema , A. de Jonge , P. Dieleman , V. Ossenkopf (2) , P. Roelfsema , J. Stutzki (2) , N. Whyborn

1 CESR - Centre d'étude spatiale des rayonnements
2 LAOG - Laboratoire d'Astrophysique de Grenoble
3 LAB - Laboratoire d'Astrophysique de Bordeaux [Pessac]
4 OASU - Observatoire aquitain des sciences de l'univers
5 UB - Université Sciences et Technologies - Bordeaux 1
6 L3AB - Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux
7 CfA - Harvard-Smithsonian Center for Astrophysics
8 LOCIE - LabOratoire proCédés énergIe bâtimEnt
9 OAA - INAF - Osservatorio Astrofisico di Arcetri
10 CSIC - Centro de Investigaciones Biológicas
11 AI PANNEKOEK - Astronomical Institute Anton Pannekoek
12 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
13 SRON - SRON Netherlands Institute for Space Research
14 OAR - INAF - Osservatorio Astronomico di Roma
15 Onsala Space Observatory
16 ESO
17 IFSI - Istituto di Fisica dello Spazio Interplanetario
18 MPIFR - Max-Planck-Institut für Radioastronomie

'Water In Star-forming regions with Herschel' (WISH) is a key programme dedicated to studying the role of water and related species during the star-formation process and constraining the physical and chemical properties of young stellar objects. The Heterodyne Instrument for the Far-Infrared (HIFI) on the Herschel Space Observatory observed three deeply embedded protostars in the low-mass star-forming region NGC1333 in several H2-16O, H2-18O, and CO transitions. Line profiles are resolved for five H16O transitions in each source, revealing them to be surprisingly complex. The line profiles are decomposed into broad (>20 km/s), medium-broad (~5-10 km/s), and narrow (<5 km/s) components. The H2-18O emission is only detected in broad 1_10-1_01 lines (>20 km/s), indicating that its physical origin is the same as for the broad H2-16O component. In one of the sources, IRAS4A, an inverse P Cygni profile is observed, a clear sign of infall in the envelope. From the line profiles alone, it is clear that the bulk of emission arises from shocks, both on small (<1000 AU) and large scales along the outflow cavity walls (~10 000 AU). The H2O line profiles are compared to CO line profiles to constrain the H2O abundance as a function of velocity within these shocked regions. The H2O/CO abundance ratios are measured to be in the range of ~0.1-1, corresponding to H2O abundances of ~10-5-10-4 with respect to H2. Approximately 5-10% of the gas is hot enough for all oxygen to be driven into water in warm post-shock gas, mostly at high velocities.

Mots clés: Astrophysics; Solar and Stellar Astrophysics

Domaines: Astrophysique stellaire et solaire [astro-ph.SR]; Astrophysique stellaire et solaire [astro-ph.SR]

L. E. Kristensen, R. Visser, E. F. van Dishoeck, U. A. Yildiz, S. D. Doty, et al.. Water in low-mass star-forming regions with Herschel: HIFI spectroscopy of NGC1333. Astronomy and Astrophysics - A&A, 2010, 521, pp.L30. ⟨10.1051/0004-6361/201015100⟩. ⟨hal-00521375⟩