Stephanie Cazaux, Thomas Geballe, Paola Caselli, Seyit Hocuk
Abstract
We propose to use GNIRS to observe CO-ice absorption at 4.7 um towards 8 sources in the Pipe Nebula. The targets are the background field stars that we have detected water ice at 3.0 um with SpeX at the IRTF. We would like to understand how the column density of CO ice grows with respect to that of water ice at the formation of first layers of ice mantles. The way that the CO-ice columns develops with water-ice will tell us what physical conditions are critical to switch the first polar ice (water-rich) formation phase to the second apolar ice (water-poor) formation phase. The targets are starless cores where we can secure the pristine compositions of ices without being altered by star formation feedback. The results will be quantitatively compared to the dust temperature and the visual extinction on the line of sights calculated based on the Herschel and 2MASS observations. This is a preparatory study for a future observation by JWST where we plan to collect corresponding CO2-ice spectra.