Polarization in young open cluster NGC 6823

TL;DR

This study presents multiwavelength polarimetric observations of stars in NGC 6823, revealing multiple dust layers, their properties, and the influence of foreground dust on polarization and reddening, with most stars showing no intrinsic polarization.

Contribution

First detailed multiwavelength polarimetric analysis of NGC 6823, identifying dust layers, their distribution, and impact on observed polarization and reddening.

Findings

Foreground dust layers are within 200 pc, closer than the cluster at 2.1 kpc.

Polarization decreases towards the outer parts of the cluster.

Grain size distribution similar to general interstellar medium.

Abstract

We present multiwavelength linear polarimetric observations of 104 stars towards the region of young open cluster NGC 6823. The polarization towards NGC 6823 is dominated by foreground dust grains and we found the evidence for the presence of several layers of dust towards the line of sight. The first layer of dust is located approximately within 200 pc towards the cluster, which is much closer to the Sun than the cluster (~ 2.1 kpc). The radial distribution of the position angles for the member stars are found to show a systematic change while the polarization found to reduce towards the outer parts of the cluster and the average position angle of coronal region of the cluster is very close to the inclination of the Galactic parallel (~ 32 degree). The size distribution of the grains within NGC 6823 is similar to those in general interstellar medium. The patchy distribution of foreground dust grains are suggested to be mainly responsible for the both differential reddening and polarization towards NGC 6823. The majority of the observed stars do not show the evidence of intrinsic polarization in their light.