Quantitative Theory of Grain Alignment: Probing Grain Environment and Grain Composition - Astrophysics > Astrophysics of GalaxiesReportar como inadecuado




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Abstract: While the problem of grain alignment was posed more than 60 years ago thequantitative model of grain alignment that can account for the observedpolarization arising from aligned grains has been formulated only recently. Thequantitative predictions of the radiative torque mechanism, which is currentlyaccepted as the dominant mechanism of grain alignment, open avenues to tracingmagnetic fields in various astrophysical environments, including diffuse anddense interstellar gas, molecular clouds, circumstellar environments, accretiondisks, comet tails, Zodiacal dust etc. At the same time, measurements of theabsolute value of polarization and its variations can, in addition, provideunique information about the dust composition and dust environment. In thereview I describe the analytical model describing well radiative torques actingon irregular grains and discuss how the alignment induced by radiative torquesvaries in the presence of superparamagnetic inclusions and pinwheel torques,e.g. arising from the molecular hydrogen formation over grain surface. I alsodescribe observations that can establish whether grains are superparamagneticand whether recoils from molecular hydrogen formations are powerful enough togive rise to substantial uncompensated torques. Answering to these questionsshould allow for reliable modeling of astrophysical polarization with numerousimportant applications, from accounting for dust contribution in CosmicMicrowave Background polarization studies to obtaining magnetic field strengthusing Chandrasekhar-Fermi technique.



Autor: A. Lazarian

Fuente: https://arxiv.org/







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