Energetic Processing of Interstellar Silicate Grains by Cosmic Rays
نویسندگان
چکیده
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. Usingmodeling, we extrapolate these results to show that 0.1Y5.0 GeV heavy-ion cosmic rays can rapidly ( 70 Myr) amorphize crystalline silicate grains ejected by stars into the interstellar medium. Subject headinggs: cosmic rays — dust, extinction Online material: color figures
منابع مشابه
Scattering by Interstellar Dust Grains . II . X - Rays
Scattering and absorption of X-rays by interstellar dust is calculated for a model consisting of carbonaceous grains and amorphous silicate grains. The calculations employ realistic dielectric functions with structure near X-ray absorption edges, with resulting features in absorption, scattering, and extinction. Differential scattering cross sections are calculated for energies between 0.3 and ...
متن کاملDetailed analysis of observed antiprotons in cosmic rays
In the present work, the origin of antiprotons observed in cosmic rays (above the atmosphere) is analyzed in details. We have considered the origin of the primaries, (which their interactions with the interstellar medium is one of the most important sources of antiprotons) is a supernova type II then used a diffusion model for their propagation. We have used the latest parameterization for anti...
متن کاملTrends in the adsorption and reactivity of hydrogen on magnesium silicate nanoclusters.
We study nanoclusters of Mg-rich olivine and pyroxene (having (MgO)6(SiO2)3 and (MgO)4(SiO2)4 compositions) with respect to their reactivity towards hydrogen atoms, using density functional calculations. Ultrasmall silicate particles are fundamental intermediates in cosmic dust grain formation and processing, and are thought to make up a significant mass fraction of the grain population. Due to...
متن کاملComposite Interstellar Grains
A composite dust grain model which is consistent with the observed interstellar extinction and linear polarization is presented. The composite grain is made up of a host silicate spheroid and graphite inclusions. The extinction efficiencies of the composite spheroidal grains for three axial ratios are computed using the discrete dipole approximation (DDA). The interstellar extinction curve is e...
متن کاملInterstellar Dust Models and Evolutionary Implications
The wavelength dependences of interstellar extinction and polarization, supplemented by observed elemental abundances and the spectrum of infrared emission from dust heated by starlight, strongly constrain dust models. One dust model that appears to be consistent with observations is presented. To reproduce the observed extinction, the model consumes the bulk of interstellar Mg, Si, and Fe (in ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2006