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 12CO10 -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.
Original language | English |
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Journal | Astronomy & Astrophysics |
Volume | 521 |
Pages (from-to) | L40 |
Number of pages | 7 |
ISSN | 0004-6361 |
DOIs | |
Publication status | Published - 1 Oct 2010 |