Energetic Processing of Interstellar Silicate Grains by Cosmic Rays

E.M. BRINGA; S.O. KUCHEYEV; M.J. LOEFFLER

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Año: 2007 vol. 662 p. 372 - 378

0004-637X

While a significant fraction of silicate dust in stellar winds has a crystalline structure, in the interstellar medium nearly all of it is amorphous. One possible explanation for this observation is the amorphization of crystalline silicates by relatively "low" energy, heavy-ion cosmic rays. Here we present the results of multiple laboratory experiments showing that single-crystal synthetic forsterite (Mg2SiO4) amorphizes when irradiated by 10 MeV Xe ions at large enough fluences. Using modeling, we extrapolate these results to show that 0.1-5.0 GeV heavy-ion cosmic rays can rapidly (~70 Myr) amorphize crystalline silicate grains ejected by stars into the interstellar medium.