TY - JOUR

T1 - Dust in the diffuse interstellar medium. Extinction, emission, linear and circular polarisation

AU - Siebenmorgen, R.

AU - Voshchinnikov, N.V.

AU - Bagnulo, S.

PY - 2014

Y1 - 2014

N2 - We present a model for the diffuse interstellar dust that explains the observed wavelength-dependence of extinction, emission, and the linear and circular polarisation of light. The model is set up with a small number of parameters. It consists of a mixture of amorphous carbon and silicate grains with sizes from the molecular domain of 0.5 up to about 500 nm. Dust grains with radii larger than 6 nm are spheroids. Spheroidal dust particles have a factor 1.5–3 greater absorption cross section in the far-infrared than spherical grains of the same volume do. Mass estimates derived from submillimetre observations that ignore this effect are overestimated by the same amount. In the presence of a magnetic field, spheroids may be partly aligned and polarise light. We find that polarisation spectra help to determine the upper particle radius of the otherwise rather unconstrained dust size distribution. Stochastically heated small grains of graphite, silicates, and polycyclic aromatic hydrocarbons (PAHs) are included.

AB - We present a model for the diffuse interstellar dust that explains the observed wavelength-dependence of extinction, emission, and the linear and circular polarisation of light. The model is set up with a small number of parameters. It consists of a mixture of amorphous carbon and silicate grains with sizes from the molecular domain of 0.5 up to about 500 nm. Dust grains with radii larger than 6 nm are spheroids. Spheroidal dust particles have a factor 1.5–3 greater absorption cross section in the far-infrared than spherical grains of the same volume do. Mass estimates derived from submillimetre observations that ignore this effect are overestimated by the same amount. In the presence of a magnetic field, spheroids may be partly aligned and polarise light. We find that polarisation spectra help to determine the upper particle radius of the otherwise rather unconstrained dust size distribution. Stochastically heated small grains of graphite, silicates, and polycyclic aromatic hydrocarbons (PAHs) are included.

KW - dust

KW - extinction – polarization – infrared: ISM – radiative transfer – instrumentation: polarimeters

U2 - 10.1051/0004-6361/201321716

DO - 10.1051/0004-6361/201321716

M3 - Article

VL - 561

SP - 1

EP - 18

JO - ASTRONOMY & ASTROPHYSICS

JF - ASTRONOMY & ASTROPHYSICS

SN - 0004-6361

IS - 1

ER -