• Ootsubo, Takafumi
• Shimonishi, Takashi
• Nashimoto, Masashi
• Hattori, Makoto
• Yamamoto, Tetsuo
• Doi, Yasuo

Abstract

We have been working on construction of the physically motivated Galactic dust emission SED models both for intensity and polarization in order to improve the detection limit of the cosmic microwave background (CMB) B-mode polarization imprinted by primordial gravitational waves. A full treatment of photon absorption processes due to quantum mechanical transitions between two-level systems (TLS) caused by deformation of lattice structure is developed to model absorption coefficients of interstellar dust grains in mm, submm and FIR wavebands. We showed that there are 8 free parameters which control shape and amplitude of emission spectrum of amorphous dust grains. Since interstellar dust consists of two main species, that is carbon and silicate, totally 16 free parameters must be defined to model interstellar dust SED at least. To construct polarization emission model from dust grains, dust grain shapes are modeled by ellipsoids. Continuous distribution of ellipsoids (CDE) is adopted as distributions of ratios of major to minor axes and major to semi-minor axes. We also showed that the degree of polarization of ellipsoidal dust depends only on the real part of the permittivity in the mm wavelength range. On the other hand, the emissivity depends on both real and imaginary parts. Therefore, the complex permittivity of interstellar dust grains is able to be constrained by measuring the frequency dependence of both degree of polarization and intensity. It provides an important clue to clarify physical nature and origin of interstellar dust grains. Our amorphous dust grain models predict that the degree of polarization of the ellipsoidal dust is monotonically decreasing function of the frequency....

Topics

• impedance spectroscopy
• amorphous
• Carbon
• grain