Facultad de Ciencias Astronómicas y Geofísicas, Observatorio Astronómico, Paseo del Bosque, 1900 La Plata, Argentina e-mail: firstname.lastname@example.org Instituto de Astrofísica de La Plata, CONICET
Accepted: 21 September 2006
We present (UBVRI ) multicolor linear polarimetric data for 31 of the brightest stars in the area of the open cluster NGC 5749 considered to study the properties of the interstellar medium (ISM) towards the cluster. Our data yield a mean polarization percentage of , close to the polarization value produced by the ISM with normal efficiency () for a mean color excess of . The mean angle of polarization vectors, , 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. Our analysis indicates that the visual absorption affecting the stars in NGC 5749 is partially produced by a dust layer located up to 300 pc from the Sun and also by a second layer of dust closer to the cluster (located at least at 700 pc). The observed photometry and our polarization data are consistent with the existence of dust within the cluster. We also show in this work how polarimetry could be an excellent technique for identifying nonmember stars.
Key words: ISM: dust, extinction / open clusters and associations: individual: NGC 5749
Based on observations obtained at Complejo Astronómico El Leoncito (CASLEO), operated under agreement between the CONICET and the National Universities of La Plata, Córdoba, and San Juan, Argentina.
© ESO, 2007