Preliminary Results from an Open Cluster Polarimetric Survey

Orsatti, A. M.; Vergne, M. M.; Feinstein, C.; Martínez, R. E.
Bibliographical reference

Exploiting Large Surveys for Galactic Astronomy, 26th meeting of the IAU, Joint Discussion 13, 22-23 August 2006, Prague, Czech Republic, JD13, #12

Advertised on:
8
2006
Number of authors
4
IAC number of authors
0
Citations
0
Refereed citations
0
Description
We present preliminary results from the Open Cluster Polarimetric Survey. The aim of the survey is to provide clues about the characteristics of the dust responsible for extinction and polarization in the light from cluster members, about its spatial distribution and also about possible memberships. Our data on linear optical polarimetry were obtained at the Complejo Astronómico "El Leoncito" (CASLEO, San Juan, Argentina). The observations were carried out using the Torino five-channel photopolarimeter attached to the 2.15-m. Each star was observed simultaneously through the Johnson-Cousins broad band UBVRI filters. At the present stage we have covered a total of 17 open clusters with galactic longitudes between l=294 and l =360 degrees in the Southern Milky Way, with a range in distance of about 800-2300 pcs, and we have observed about 500 individual stars. For each of these open clusters, we have been able to detect the presence (if any) of intracluster dust and the interstellar dust distribution on direction to the cluster, with auxiliary observations of non-member stars on the same direction. Other information we got from the polarimetric observations is the mean grain size of the dust clouds and the mean direction of the magnetic field at the clusters position. Additionally, the polarimetry data can be used as a powerful criterion for determining the membership in a galactic cluster and for detecting the location of an energetic phenomenon occurred in the past of a cluster. A very important by-product of these studies is the isolation of stars displaying polarization of a non-interstellar origin: that is, stars with extended atmospheres (like Be stars), dust associated to possible binary systems, or surrounding the star (due to evolution or as a formation remnant). In the present study we will emphasize about: 1)Spatial distribution of the observed open clusters 2)General polarimetric characteristics of the nearby dust clouds 3)Distribution of the dust clouds on the line of sight to the clusters 4) stars with intrinsic polarization and their general characteristics.