Abstract :
Exploring the structure and origin of our Milky Way galaxy stands as a primary objective in the realm of Galactic astronomy. Our location inside the Galaxy provides a unique advantage to investigate individual stars in great detail. However, our vantage point within the Disk presents challenges in mapping its complete structure. Nevertheless, many attempts have been made to unravel the different structural components of our Galaxy. While it is well know that the Milky Way is a barred spiral galaxy, the finer details like the number of arms, their position, and extent are still highly debated. In order to map our galactic disk in more detail, we extracted the largest catalogue of 8.8 million red clump stars from 2MASS colour-magnitude diagrams in the Galactic disk. The resulting distribution of red clump stars in the Galactic plane revealed the distant feature: the Outer arm of the Galaxy with an extension of 6 kpc beyond previously established extent.
In addition to stars, we explore the use of interstellar dust, primarily confined to the Galactic disk, as a means to trace the intricate structures across small and large scales. Departing from conventional extinction-based methodologies, we utilised interstellar polarisation, a directly measured quantity of interstellar dust along with the distance information from Gaia to unravel the dust distribution in different lines of sight. The polarisation observations of a total of fifteen Galactic open clusters were carried out in three different sight-lines from meter-class telescopes to demonstrate the usefulness of ISM polarisation in deciphering the dust distribution and morphology of the disk. Our polarisation measurement not only shed light on small scale and large scale structure but also provide the strong evidences of the alignment of the large-scale magnetic field. A brief description of all the results will be presented in the seminar.
