Optical polarimetric study of open clusters: Distribution of Interstellar matter towards NGC 654

TL;DR

This study uses optical polarimetry to analyze the distribution and properties of interstellar dust layers along the line of sight to the open cluster NGC 654, revealing multiple dust layers with distinct magnetic field orientations.

Contribution

It provides new polarimetric data and evidence for two separate dust layers at different distances, enhancing understanding of interstellar matter distribution towards NGC 654.

Findings

Identification of two dust layers at ~200 pc and ~1 kpc.

Both dust layers have magnetic fields aligned with the Galactic plane.

Foreground dust has a ring morphology with a central hole.

Abstract

We present new B, V and R linear polarimetric observations for 61 stars towards the region of the young open cluster NGC 654. In this study we found evidence for the presence of at least two layers of dust along the line of sight to the cluster. The distances to the two dust layers are estimated to be ~ 200 pc and ~ 1 kpc which are located much closer to the Sun than the cluster (~ 2.4 kpc). Both the dust layers have their local magnetic field orientation nearly parallel to the direction of the Galactic plane. The foreground dust layer is found to have a ring morphology with the central hole coinciding with the center of the cluster. The foreground dust grains are suggested to be mainly responsible for both the observed differential reddening and the polarization towards the cluster.