Herschel-HIFI observations of high-J CO lines in the NGC 1333 low-mass star-forming region

U.A. Y{\i}ld{\i}z , E.F. van Dishoeck , L.E. Kristensen , R. Visser , J.K. J{\o}rgensen , G.J. Herczeg , T.A. van Kempen , M.R. Hogerheijde

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S.D. Doty A.O. Benz S. Bruderer S.F.Wampfler E. Deul R. Bachiller A. Baudry M. Benedettini E. Bergin P. Bjerkeli G.A. Blake S. Bontemps J. Braine P. Caselli J. Cernicharo C. Codella F. Daniel A.M. di Giorgio C. Dominik P. Encrenaz M. Fich A. Fuente T. Giannini J.R. Goicoechea Th. de Graauw F. Helmich F. Herpin T. Jacq D. Johnstone B. Larsson D. Lis R. Liseau F.-C. Liu M. Marseille C. McCoey G. Melnick D. Neufeld B. Nisini M. Olberg B. Parise J.C. Pearson R. Plume C. Risacher J. Santiago-Garcia P. Saraceno R. Shipman M. Tafalla A. G. G. M. Tielens F. van der Tak F. Wyrowski P. Dieleman W. Jellema V. Ossenkopf R. Schieder J. Stutzki

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classification 🌌 astro-ph.SR

keywords linesiraslow-massobservationsaroundc18oevaporationfwhm

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Herschel-HIFI observations of high-J lines (up to J_u=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 (FWHM 5-10 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.

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Herschel-HIFI observations of high-J CO lines in the NGC 1333 low-mass star-forming region

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