ENERGETIC PROCESSES REVEALED BY SPECTRALLY RESOLVED HIGH-J CO LINES IN LOW-MASS STAR-FORMING REGIONS WITH HERSCHEL-HIFI.

Herschel-HIFI observations of high-J lines (up to J_u = 10) of ¹²CO, ¹³CO and C¹⁸O are presented toward three deeply embed- ded low-mass protostars in NGC 1333. The observations show several energetic components including shocked and quiescent gas. Radiative transfer models are used to quantify the C¹⁸O envelope abundance which require a jump in the abundance at an evaporation temperature, Tev ~ 25 K, providing new direct evidence of a CO ice evaporation zone around protostars. The abundance in the outermost part of the enve- lope, X₀, is within the canonical value of 2 x 10^-4; however the inner abundance, Xin, is found around a factor of 3-5 lower than X₀. [ABSTRACT FROM AUTHOR]