| Description |
This proposal is presented by the SPIRE SAG4 consortium associated with HIFI experts for a specific follow-up of two SPIRE FTS recently observed sources map for the HII compact sources G29.96-0.02 and G32.80+0.19. Naylor et al. (2010) report the detection of the fundamental rotational transition of CH+, in absorption against the compact source continuum, due to its presence in the the diffuse interstellar medium. These detections are important to shed light on the formation processes and on the occurence of CH+, which are still outstanding questions in astrophysics. For a better understanding of CH+ associated diffuse medium chemistry and to effectively be able to spectrally resolve the components along the line of sight, a follow-up with a good signal-to-noise (above 30) with HIFI is mandatory. We need the HIFI capabilities to separate CH+ emission and absorption, to derive the kinematics of the absorptions, to assign them to individual interstellar components, and to extract r^ant column densities by properly taking into account saturation effects. We wish to sample two galactic lines of sights using the two compact sources as background, to complement SPIRE FTS observations already performed. These two sources offer not only a scientific goal to follow CH and CH+ in the diffuse medium but also a unique opportunity to cross calibrate the SPIRE FTS and HIFI Herschel instruments with a moderate amount of integration time. In this proposal, we ask for 2 hours of total integration time. |
