Modelling polarization properties of comet 1P/Halley using a mixture of compact and aggregate particles

Abstract

Recently, the result obtained from `Stardust' mission suggests that the overall ratio of compact to aggregate particles is 65:35 (or 13:7) for Comet 81P/Wild 2 (Burchell et al. 2008). In the present work, we propose a model which considers cometary dust as a mixture of compact and aggregate particles, with composition of silicate and organic. We consider compact particles as spheroidal particles and aggregates as BCCA and BAM2 aggregate with some size distribution. For modeling Comet 1P/ Halley, the power-law size distribution n(a)= a^{-2.6}, for both compact and aggregate particles is taken. We take a mixture of BAM2 and BCCA aggregates with a lower and upper cutoff size around 0.20$\mu m$ and 1$\mu m$. We also take a mixture of prolate, spherical and oblate compact particles with axial ratio (E) from 0.8 to 1.2 where a lower and upper cutoff size around 0.1$\mu m$ and 10$\mu m$ are taken. Using T-matrix code, the average simulated polarization curves are generated which can best fit the observed polarization data at the four wavelengths $\lambda$ = 0.365$\mu m$, 0.485$\mu m$, 0.670$\mu m$ and 0.684$\mu m$. The suitable mixing percentage of aggregates emerging out from the present modeling corresponds to 50% BAM2 and 50% BCCA particles and silicate to organic mixing percentage corresponds to 78% silicate and 22% organic in terms of volume. The present model successfully reproduces the observed polarization data, especially the negative branch, more effectively as compared to other work done in the past. It is found that among the aggregates, the BAM2 aggregate plays a major role, in deciding the cross-over angle and depth of negative polarization branch.

7 pages, 5 figures (accepted for publication in MNRAS on May 4, 2011)

References in corpus (1)

• Modeling Porous Dust Grains with Ballistic Aggregates I: Geometry and Optical Properties

Cited by in corpus (13)

• Discovery of a relation between black hole mass and soft X-ray time lags in active galactic nuclei
• Time lags in the ultraluminous X-ray source NGC 5408 X-1: implications for the black hole mass
• A combined timing/spectral study of IRAS 13224-3809 using XMM-Newton data
• Testing the X-ray reverberation model KYNREFREV in a sample of Seyfert 1 Active Galactic Nuclei
• 1ES 1927+654: a bare Seyfert 2
• Dependence of light scattering properties on porosity, size and composition of dust aggregates
• Modelling heterogeneous dust particles. An application to cometary polarization
• Polarimetric studies of Comet C/2009 P1 (Garradd)
• The effect of porosity of dust particles on polarization and color with special reference to comets
• Imaging polarimetry of comets C/2013 V1 (Boattini) and 290P/Jager before and after perihelion
• X-ray time delays from the Seyfert 2 galaxy IRAS 18325-5926
• Imaging polarimetry of Comet C/2012 L2 (LINEAR)
• Java application for the superposition T-matrix code to study the optical properties of cosmic dust aggregates