Large Interstellar Polarisation Survey II. UV/optical study of cloud-to-cloud variations of dust in the diffuse ISM

Understand

It is well known that the dust properties of the diffuse interstellar medium exhibit variations towards different sight-lines on a large scale.

• We have investigated the variability of the dust characteristics on a small scale, and from cloud-to-cloud.
• We use low-resolution spectro-polarimetric data obtained in the context of the Large Interstellar Polarisation Survey (LIPS) towards 59 sight-lines in the Southern Hemisphere, and we fit these data using a dust model composed of silicate and carbon particles with sizes from the molecular to the sub-micrometre domain.
• Large (> 6 nm) silicates of prolate shape account for the observed polarisation.