Optical polarization observations in the region of Stock 16

We present (UBVRI) multicolor linear polarimetric data for 26 of the brightest stars in the area of the open cluster Stock 16 that were considered to study the properties of the ISM (interstellar medium) towards the cluster. Our data yield a mean polarization percentage of $P\sim2.5\%$, close to the polarization value produced by the ISM with normal efficiency ($P_{\lambda_{\rm max}} \sim 5 E_{B-V}$) undergoing a color excess of $E_{B-V} =0.51$. The mean angle of the polarization vectors, $\theta= 74\fdg9$, agrees quite well with the expected angle produced by dust particles aligned in the direction of the galactic disk (and the magnetic field) in the region. A study of the extinction suffered by the stars in the zone was also performed combining our new data with previous photometric data. In this sense, our analysis indicates that the visual absorption affecting Stock 16 stars is mainly produced in front of the cluster by a dust cloud at approximately 500 pc from the sun. The large polarization value of the nonmember star, WR 51, confirms its background star nature