Variations in H2O+/H2O ratios toward massive star-forming regions

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

1 MPIFR - Max-Planck-Institut für Radioastronomie
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 SRON - SRON Netherlands Institute for Space Research
8 OAA - INAF - Osservatorio Astrofisico di Arcetri
9 LOCIE - LabOratoire proCédés énergIe bâtimEnt
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 OAR - INAF - Osservatorio Astronomico di Roma
14 Onsala Space Observatory
15 CESR - Centre d'étude spatiale des rayonnements
16 ESO
17 IFSI - Istituto di Fisica dello Spazio Interplanetario
18 LRA - Laboratoire de Radioastronomie

Early results from the Herschel Space Observatory revealed the water cation H2O+ to be an abundant ingredient of the interstellar medium. Here we present new observations of the H2O and H2O+ lines at 1113.3 and 1115.2 GHz using the Herschel Space Observatory toward a sample of high-mass star-forming regions to observationally study the relation between H2O and H2O+ . Nine out of ten sources show absorption from H2O+ in a range of environments: the molecular clumps surrounding the forming and newly formed massive stars, bright high-velocity outflows associated with the massive protostars, and unrelated low-density clouds along the line of sight. Column densities per velocity component of H2 O+ are found in the range of 10^12 to a few 10^13 cm-2 . The highest N(H2O+) column densities are found in the outflows of the sources. The ratios of H2O+/H2O are determined in a range from 0.01 to a few and are found to differ strongly between the observed environments with much lower ratios in the massive (proto)cluster envelopes (0.01-0.1) than in outflows and diffuse clouds. Remarkably, even for source components detected in H2O in emission, H2O+ is still seen in absorption.

Mots clés: Astrophysics; Galaxy Astrophysics

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

F. Wyrowski, F. van Der Tak, Fabrice Herpin, Alain Baudry, Sylvain Bontemps, et al.. Variations in H2O+/H2O ratios toward massive star-forming regions. Astronomy and Astrophysics - A&A, 2010, 521, pp.L34. ⟨10.1051/0004-6361/201015110⟩. ⟨hal-00521348⟩