Herschel/HIFI observations of high-J CO lines in the NGC 1333 low-mass star-forming region
de Graauw, Th.; Liseau, R.; Braine, J.; Codella, C.; Dominik, C.; Schieder, R.; Ossenkopf, V.; Bontemps, S.; Benedettini, M.; van Dishoeck, E. F.; Bachiller, R.; Larsson, B.; Blake, G. A.; Cernicharo, J.; Daniel, F.; Encrenaz, P.; Goicoechea, J. R.; Johnstone, D.; Pearson, J. C.; Plume, R.; Stutzki, J.; Olberg, M.; Melnick, G.; Tielens, A. G. G. M.; Risacher, C.; Fuente, A.; Benz, A. O.; Bruderer, S.; van der Tak, F.; Wyrowski, F.; Shipman, R.; Dieleman, P.; Fich, M.; Herpin, F.; Jellema, W.; McCoey, C.; Bjerkeli, P.; Marseille, M.; Nisini, B.; Caselli, P.; Lis, D.; Kristensen, L. E.; Hogerheijde, M. R.; Tafalla, M.; Giannini, T.; Neufeld, D.; Saraceno, P.; Herczeg, G. J.; Wampfler, S. F.; Doty, S. D.; Baudry, A.; Bergin, E.; di Giorgio, A. M.; Helmich, F.; Jacq, T.; Jørgensen, J. K.; Parise, B.; Santiago-García, J.; van Kempen, T. A.; Visser, R.; Yıldız, U. A.; Deul, E.; Liu, F. -C.
Netherlands, Germany, Denmark, United States, Switzerland, Spain, France, Italy, Sweden, United Kingdom, Canada
Abstract
Herschel/HIFI observations of high-J lines (up to Ju = 10) of 12CO, 13CO and C18O are presented toward three deeply embedded low-mass protostars, NGC 1333 IRAS 2A, IRAS 4A, and IRAS 4B, obtained as part of the Water In Star-forming regions with Herschel (WISH) key program. The spectrally-resolved HIFI data are complemented by ground-based observations of lower-J CO and isotopologue lines. The 12CO 10-9 profiles are dominated by broad (FWHM 25-30 km s-1) emission. Radiative transfer models are used to constrain the temperature of this shocked gas to 100-200 K. Several CO and 13CO line profiles also reveal a medium-broad component (FWHM5-10 km s-1), seen prominently in H2O lines. Column densities for both components are presented, providing a reference for determining abundances of other molecules in the same gas. The narrow C18O 9-8 lines probe the warmer part of the quiescent envelope. Their intensities require a jump in the CO abundance at an evaporation temperature around 25 K, thus providing new direct evidence for a CO ice evaporation zone around low-mass protostars.
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendices and acknowledgements (pages 5 to 7) are only available in electronic form at http://www.aanda.org