Abstract Ionization is a major driver of both physical and chemical evolution in protostellar systems. Recent observations reveal substantial chemical processing in protoplanetary disks by the time the surrounding envelope has cleared. Thus, physical conditions during the preceding phase, when an infalling envelope of material is still present, are crucial for determining the extent of chemical processing at early stages. We used observations of H 13 CO + and C 18 O from the Northern Extended Millimeter Array and Institut de Radioastronomie Millimétrique (IRAM) 30 m telescope to constrain the ionization rate in the envelopes of three Class 0 protostars: NGC-1333 IRAS4A, L1448-C, and L1157. We find ionization rates in the range ζ = 10 −16 –10 −13 s −1 , several orders of magnitude above the ionization rate of ζ = 6 × 10 −17 s −1 in the diffuse interstellar medium. This supports the idea that ionization driven chemistry is more efficient at earlier stages (<10 5 yr) of protostellar evolution.
Schwarz et al. (Tue,) studied this question.