Name: Sadhana Singh
Affiliation: Aryabhatta Research Institute of Observational Sciences
Conference ID : ASI2022_351
Title : Polarization, Polarizing Efficiency, and Grain alignment towards the direction of the cluster NGC 2345
Authors : Sadhana Singh, Jeewan C. Pandey, Thiem Hoang
Abstract Type: Poster
Abstract Category : Stars, ISM and Galaxy
Abstract : The starlight passing through the interstellar medium (ISM) becomes linearly polarized due to the differential extinction from the alignment of asymmetric dust grains in the ISM. The polarimetric study will be an effective tool for providing information about the magnetic field orientation, also it reveal information about the properties of ISM dust grains and their alignment. I would like to present the grain alignment and dust properties towards the direction of the cluster NGC 2345 using the multi-band 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% and 0.58 micron, respectively. This reveals a similar size distribution of dust grains to that in the general interstellar medium in the direction of NGC 2345. An indication of the dust layer of visual extinction around 1.15 mag close to a distance of 1.2 kpc towards the line-of-sight of the cluster NGC 2345 is found. The dust grains located away from this layer are found to be aligned with the Galactic magnetic field, whereas a different orientation of the dust grains lying in the foreground of this layer is found. Polarizing efficiency of grains in this direction is found to be close to the average efficiency for our Galaxy. 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.