1 research outputs found
Interstellar OH+, H2O+ and H3O+ along the sight-line to G10.6-0.4
We report the detection of absorption lines by the reactive ions OH+, H2O+
and H3O+ along the line of sight to the submillimeter continuum source
G10.60.4 (W31C). We used the Herschel HIFI instrument in dual beam switch
mode to observe the ground state rotational transitions of OH+ at 971 GHz, H2O+
at 1115 and 607 GHz, and H3O+ at 984 GHz. The resultant spectra show deep
absorption over a broad velocity range that originates in the interstellar
matter along the line of sight to G10.60.4 as well as in the molecular gas
directly associated with that source. The OH+ spectrum reaches saturation over
most velocities corresponding to the foreground gas, while the opacity of the
H2O+ lines remains lower than 1 in the same velocity range, and the H3O+ line
shows only weak absorption. For LSR velocities between 7 and 50 kms we
estimate total column densities of (OH+) cm,
(H2O+) cm and (H3O+) cm. These detections confirm the role of O and OH in
initiating the oxygen chemistry in diffuse molecular gas and strengthen our
understanding of the gas phase production of water. The high ratio of the OH+
by the H2O+ column density implies that these species predominantly trace
low-density gas with a small fraction of hydrogen in molecular form