Porous and Fluffy Grains in the Regions of Anomalous Extinction

Journal of astrophysics and astronomy

R. Gupta³  J. N. Desai¹  B. G. Anandarao¹  D. B. Vaidya² 

[1] Physical Research Laboratory, Ahmedabad 380 009, India.$$;Gujarat College, Ahmedabad 380 006, India.$$;Inter-University Centre for Astronomy & Astrophysics, Pune 411007, India.$$

关键词: Interstellar dust;    extinction;    porous grains;    anomalous extinction.;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

It has long been established that the ratio of total to selective extinction is anomalously large (≥ 5) in certain regions of the interstellar medium. In these regions of anomalous extinction the dust grains are likely to be irregular in shape and fluffy in structure. Using discrete dipole approximation (DDA) we calculate the extinction for porous and fluffy grains. We apply DDA first to solid spheroidal particles assumed to be made of a certain (large) number of dipoles. Then we systematically reduce the number of dipoles to model the porous grains. The aggregates of these particles are suggested to form the fluffy grains. We study the extinction for these particles as a function of grain size, porosity and wavelength. We apply these calculations to interpret the observed extinction data in the regions of star formation (e.g. the Orion complex).

【 授权许可】

Unknown