The Puppis OB III association: polarization measurements

Abstract

Optical linear polarization measurements of association members and field stars in the region of the Puppis OB III association are presented. The association members are found to have larger values of polarization than the field stars.In the direction of the association there are two regions of polarizing interstellar medium with magnetic fields that are nearly at right angles to each other. The observed ratio of polarization to reddening for stars in this direction is about a factor of 3 smaller than the mean interstellar value indicating either a very poor efficiency of dust grain alignment, or a magnetic field configuration that is predominantly longitudinal.