Abstract Details

Name: Sadhana Singh
Affiliation: ARIES
Conference ID: ASI2020_158
Title : Optical Polarization Study in the Cluster NGC 1817
Authors and Co-Authors : Sadhana Singh, Jeewan C. Pandey
Abstract Type : Poster
Abstract Category : Stars, ISM and Galaxy
Abstract : In order to get the information about properties of interstellar medium (ISM) dust, we are using polarization technique. According to Davis & Greenstein (1951), the polarization of starlight is caused by the selective extinction due to the elongated dust grains aligned in space possibly due to the magnetic field. As the grains are thought to align due to the local magnetic field, the observed polarization vectors will help to map the general geometry of the magnetic field. Also, wavelength dependence of polarization gives information about the size distribution of dust grains. From the polarimetric study, the information regarding dust grains (shape, size, alignment, and polarizing efficiency) and the foreground dust contribution can be revealed. Here, we would like to present results for the open star cluster NGC 1817 in B, V, R, and I bands. We have observed the cluster using Aries IMaging POLarimeter (AIMPOL) mounted as back-end instrument at the 104-cm Sampuranand telescope at ARIES, Nainital. Weighted mean values of degree of polarization are found to be 0.64, 0.88, 0.84, and 0.51 % and position angle are found to be 138, 120, 119, and 118 degrees, in B, V, R, and I bands, respectively. We have found that the size distribution of the dust grains towards the cluster NGC 1817 is similar to those in the general ISM as the value of wavelength corresponding to maximum polarization lies nearly at 0.55 micron. The polarization towards NGC 1817 is dominated by foreground dust grains which are aligned possibly due to Galactic magnetic field. Apart from these, we have also used linear polarization data to differentiate between members and non-members of the cluster NGC 1817.