| Authors Affiliation: | 1 Physical Research Laboratory, Ahmedabad-380009, India
2 Inter-University Institute For High Energies, Université Libre de Bruxelles, Brussels-1050, Belgium
3 Aryabhatta Research Institute of Observational Sciences, Nainital-263001, India
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| Abstract : | The distribution of interstellar dust plays a crucial role in shaping our understanding of the morphology of the Milky Way galaxy. Dust is confined to the Galactic disk, making it an ideal candidate for mapping the structure and, specifically, the spiral arms of the Galaxy. Interstellar dust emits thermal radiation primarily in longer wavelengths. However, estimating distances required to study the 3D dust distribution relies on kinematic methods, which exhibit significant uncertainties, especially towards the centre and anti-centre directions. Nevertheless, the effects of interstellar dust, such as extinction and polarisation, can be utilised as indirect probes of dust distribution. The starlight gets partially plane-polarised after passing through the asymmetrical and magnetically aligned dust grains. Combining the polarisation data with distance information of stars can provide the direct observational signature of dust distribution along a line of sight (e.g., Uppal et al., 2022; Pelgrims et al., 2023). In our study, we targeted Galactic open clusters present towards the anti-centre direction. We selected clusters in the same line of sight but located at different distances in order to determine the number of dust layers and their distances in that sightline. The outer Galaxy is expected to have less dust density, providing us with a unique opportunity to observe clusters at greater distances. We observed five open clusters, including Kronberger 1, Berkeley69, Berkeley71, Berkeley 19, and King 8, spanning a range of 2.1 to 6.2 kpc distances (Cantat-Gaudin et al., 2018) from 1.04m Sampurnanand telescope using the ARIES imaging polarimeter (AIMPOL). We developed automated pipelines for efficient reduction and analysis of the observed data. By combining our polarisation results with the distance information derived from Gaia parallaxes, we found evidence of large-scale dust features corresponding to the spiral arms, i.e., Perseus and Outer spiral arms, towards the anti-centre direction. |
