Variations in H2O+/H2O ratios toward massive star-forming regions
Abstract
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.
Keywords
Cite
@article{arxiv.1007.4370,
title = {Variations in H2O+/H2O ratios toward massive star-forming regions},
author = {F. Wyrowski and F. van der Tak and F. Herpin and A. Baudry and S. Bontemps and L. Chavarria and W. Frieswijk and T. Jacq and M. Marseille and R. Shipman and E. F van Dishoeck and A. O. Benz and P. Caselli and M. R. Hogerheijde and D. Johnstone and R. Liseau and R. Bachiller and M. Benedettini and E. Bergin and P. Bjerkeli and G. Blake and J. Braine and S. Bruderer and J. Cernicharo and C. Codella and F. Daniel and A. M. di Giorgio and C. Dominik and S. D. Doty and P. Encrenaz and M. Fich and A. Fuente and T. Giannini and J. R. Goicoechea and Th. de Graauw and F. Helmich and G. J. Herczeg and J. K. Jørgensen and L. E. Kristensen and B. Larsson and D. Lis and C. McCoey and G. Melnick and B. Nisini and M. Olberg and B. Parise and J. C. Pearson and R. Plume and C. Risacher and J. Santiago and P. Saraceno and M. Tafalla and T. A. van Kempen and R. Visser and S. Wampfler and U. A. Yıldız and J. H. Black and E. Falgarone and M. Gerin and P. Roelfsema and P. Dieleman and D. Beintema and A. De Jonge and N. Whyborn and J. Stutzki and V. Ossenkopf},
journal= {arXiv preprint arXiv:1007.4370},
year = {2015}
}
Comments
5 pages, 4 figures, accepted for publication as a letter in the A&A Herschel-HIFI special issue