The onset of energetic particle irradiation in Class 0 protostars

Author: Favre C.   López-Sepulcre A.   Ceccarelli C.   Dominik C.   Caselli P.   Caux E.   Fuente A.   Kama M.   Le Bourlot J.   Lefloch B.   Lis D.   Montmerle T.   Padovani M.   Vastel C.  

Publisher: Edp Sciences

E-ISSN: 1432-0746|608|issue|A82-A82

ISSN: 0004-6361

Source: Astronomy & Astrophysics, Vol.608, Iss.issue, 2017-12, pp. : A82-A82

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Abstract

Context. The early stages of low-mass star formation are likely to be subject to intense ionization by protostellar energetic MeV particles. As a result, the surrounding gas is enriched in molecular ions, such as HCO+ and N2H+. Nonetheless, this phenomenon remains poorly understood for Class 0 objects. Recently, based on Herschel observations taken as part of the key programme Chemical HErschel Surveys of Star forming regions (CHESS), a very low HCO+/N2H+ abundance ratio of about three to four, has been reported towards the protocluster OMC-2 FIR4. This finding suggests a cosmic-ray ionization rate in excess of 10-14 s-1, much higher than the canonical value of ζ = 3 × 10-17 s-1 (value expected in quiescent dense clouds).