Multicolor polarization study of Ara OB1

We present the results of a multicolor polarimetric study of stars in the a ssociation Ara OB1. Several objects belonging to the clusters NGC 6204, 619 3, and 6167 and the local field were observed as part of a global study of the region. The polarimetry shows that the orientation of the polarimetric vectors of each star is very similar within each cluster. The average value s are 35 degrees 5 +/- 15 degrees 1 and 52 degrees 2 +/- 16 degrees for NGC 6204 and 6193, respectively. An average value of 106 degrees 5 +/- 9 degre es 9 is found for NGC 6167,but the angle distribution is asymmetric, and a second component can be fitted to the angle histogram (P.A. similar to 120 degrees 8 +/- 11 degrees 6), showing a behavior not observed in NGC 6204 an d 6193. So, we suggest that some of the observed stars perhaps belong to an other stars grouping, located behind NGC 6167 and between a dust layer with a different orientation of the grains. The large difference in the polariz ation angle between NGC 6167 and the other two clusters could also be expla ined because NGC 6167 is supposed to be at the center of a gas-expanding st ructure and it is possible that this cluster was the origin of the star for mation process in the Ara OB1 association, triggered by stellar winds or su pernova explosions.