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

F. Wyrowski*, F. van der Tak, F. Herpin, A. Baudry, S. Bontemps, L. Chavarria, W. Frieswijk, T. Jacq, M. Marseille, R. Shipman, E. F. van Dishoeck, A. O. Benz, P. Caselli, M. R. Hogerheijde, D. Johnstone, R. Liseau, R. Bachiller, M. Benedettini, E. Bergin, P. BjerkeliG. Blake, J. Braine, S. Bruderer, J. Cernicharo, C. Codella, F. Daniel, A. M. di Giorgio, C. Dominik, S. D. Doty, P. Encrenaz, M. Fich, A. Fuente, T. Giannini, J. R. Goicoechea, Th de Graauw, F. Helmich, G. J. Herczeg, J. K. Jørgensen, L. E. Kristensen, B. Larsson, D. Lis, C. McCoey, G. Melnick, B. Nisini, M. Olberg, B. Parise, J. C. Pearson, R. Plume, C. Risacher, J. Santiago, P. Saraceno, M. Tafalla, T. A. van Kempen, R. Visser, S. Wampfler, U. A. Yıldız, J. H. Black, E. Falgarone, M. Gerin, P. Roelfsema, P. Dieleman, D. Beintema, A. de Jonge, N. Whyborn, J. Stutzki, V. Ossenkopf

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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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 H2O+ 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.

Original languageEnglish
Article numberL34
Number of pages5
JournalAstronomy & astrophysics
Publication statusPublished - Oct-2010


  • ISM: clouds
  • ISM: molecules
  • submillimeter: ISM
  • stars: formation
  • LINE
  • DR21
  • HIFI
  • W51

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