Broad-band optical polarimetric studies towards the Galactic young star cluster Berkeley 59

Abstract

We present multiwavelength optical linear polarimetric observations of 69\nstars toward the young open cluster Be 59. The observations reveal the presence\nof three dust layers located at the distances of \\sim300, \\sim500 and \\sim700\npc. The dust layers produce a total polarization Pv \\sim 5.5 per cent. The mean\nvalues of polarization and polarization angles due to the dust layers are found\nto increase systematically with distance. We show that polarimetry in\ncombination with the (U - B) - (B - V) colour-colour diagram yields a better\nidentification of cluster members. The polarization measurements suggest that\nthe polarization due the intra-cluster medium is \\sim 2.2 per cent. An\nanomalous reddening law exists for the cluster region, indicating a relatively\nlarger grain size than that in the diffuse ISM. The spatial variation of the\npolarization and E(B - V) is found to increase with radial distance from the\ncluster center, whereas the {\\theta}v and {\\lambda}max are found to decrease\nwith increasing radial distance from the cluster center. About 40 per cent of\ncluster members show the signatures of either intrinsic polarization or\nrotation in their polarization angles. There is an indication that the star\nlight of the cluster members might have been depolarized because of non-uniform\nalignment of dust grains in the foreground dust layers and in the intra-cluster\nmedium.\n