Interstellar extinction and polarization: some theoretical results

Tables give parameters of interstellar extinction and polarization curves produced by rotating homogeneous spheroids with imperfect Davis-Greenstein (IDG) orientation.

  • table 1 (amorphous carbon, oblate particles with a/b=2.0)
  • table 2 (amorphous carbon, oblate particles with a/b=4.0)
  • table 3 (amorphous carbon, prolate particles with a/b=2.0)
  • table 4 (amorphous carbon, prolate particles with a/b=4.0)
For model description and some results see:

Das H.K., Voshchinnikov N.V., Il'in V.B.
Interstellar extinction and polarization - A spheroidal dust grain approach perspective.
Monthly Notices of Royal Astronomical Society, v.404, 265-274 (2010).
(available here)

Voshchinnikov N.V., Yakovlev I.S.
The relationship between grain shape and interstellar polarization. In: Muinonen K. et al. (eds),
Electromagnetic and Light Scattering: Theory and Applications, XII, pp. 318-321 (2010).
(available here)

Input parameters:


Type of spheroid (prolate/oblate)

a/b - aspect ratio

r_v,min - minimum size in power-law size distribution
(r_v radius of a sphere whose volume is equal to that of spheroid)

r_v,max - maximum size in power-law size distribution

q0 - power degree

idg - type of orientation 1/2=pdg/idg (imperfect/perfect Davis-Greenstein)

del0 - degree of alignment

Omega - angle between the line of sight and the magnetic field direction

Output parameters:

R_V - total-to-selective extinction ratio

P/E(B-V) - polarizing efficiency of the interstellar medium
(ratio of the maximum degree of linear polarization P_max to colour excess)

IMPORTANT! Very large values of P/E(B-V) for a given model result from
two facts: 1) colour excess E(B-V) is small (grey extinction) and/or
2) P(lam_max)>>P(V) and lam_max is far from the V band.

lam_max - wavelength corresponding to P_max

W - width of linear polarization curve


asil_D03 - astronomical silicate (B.T. Draine, ApJ, 598, 1026, 2003).

AC-Be - amorphous carbon (V.G. Zubko et al., MNRAS, 282, 1321, 1996).