Abstract:
We have investigated the grain alignment and dust properties towards the direction of the cluster NGC 2345 using the multiband
optical polarimetric observations. For the majority of the stars, the observed polarization is found to be due to the interstellar
medium with average values of maximum polarization and wavelength corresponding to it as 1.55 per cent and 0.58 μm,
respectively. This reveals a similar size distribution of dust grains to that in the general interstellar medium in the direction of
NGC 2345. Alteration of dust properties near the distance of 1.2 kpc towards the direction of NGC 2345 has been noticed. The
dust grains located beyond this distance are found to be aligned with the Galactic magnetic field, whereas a dispersion in the
orientation of the dust grains lying in the foreground of this distance is found. Polarizing efficiency of grains in this direction is
found to be close to the average efficiency for our Galaxy. The decreased grain size along with the increased polarizing efficiency
towards the core region of the cluster indicates the local radiation field is higher within the cluster, which is responsible for the
increased alignment efficiency of small grains. The wavelength of maximum polarization (associated with the average size of
aligned grains) is also found to increase with extinction and reduces with the increase in polarizing efficiency, which can be
explained by the radiative torque alignment mechanism.
