The HIFI instrument on Herschel provides a unique opportunity to undertake an astronomical study of light negative molecular ions in the interstellar gas, as these are difficult or impossible to observe from ground based observatories. A sensitive search for the negative ions CN-, CCH-, and OH- with HIFI toward 6 galactic molecular sources is proposed. Three successive rotational transitions (J=6, 7, 8) of CN- and CCH- in HIFI bands 1 - 3, and the lowest rotational transition of OH- near 1.12 THz will be observed. The goals of this study are: i. to enlarge the number of known sources of light negative molecular ions; ii. to determine the abundances of the anions, as well as the anion-to-neutral ratios to assess theoretical models of the fractional ionization of molecular clouds; and iii. to assess the chemical environment of anions through parallel observations of neutral molecules (H13CN and HNC) and positive molecular ions (CO+ and H13CO).
Publication
Instrument
HIFI_HifiPoint_dbs
Temporal Coverage
2011-04-21T23:45:27Z/2013-03-26T04:14:22Z
Version
SPG v14.2.0
Mission Description
Herschel was launched on 14 May 2009! It is the fourth cornerstone mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
European Space Agency, gupta et al., 2013, 'A Study of the Small Negative Molecular Ions CN-, CCH-, and OH- in the Interstellar Gas', SPG v14.2.0, European Space Agency, https://doi.org/10.5270/esa-56g6fxc
