Bibcode
Vergne, M. M.; Martínez, R.; Feinstein, C.
Referencia bibliográfica
Boletín de la Asociación Argentina de Astronomía, vol.46, p.74
Fecha de publicación:
0
2003
Número de citas
0
Número de citas referidas
0
Descripción
We present new (UBVRI) multicolor linear polarimetric data for 22 of the
brightest stars in the area of the open clusters Hogg 22 and NGC 6204
with the aim of studying the properties of the ISM (interstellar
medium) toward
these clusters and between them. The new data were incorporated to our
data set of previously taken observations (Waldhausen et al. 1999),
resulting the total number of 28 observed stars in the region. Our data
yield for NGC 6204 a mean polarization percentage of
Pλ_max˜1.8%, close to the polarization value
produced by the ISM with normal efficiency
(Pλ_max ˜ 5 EB-V) with a color excess
of EB-V =0.51. Meanwhile for Hogg 22, located
behind NGC 6204, the mean polarization
found is Pλ_max˜ 2.15%, lower than the expected
value
for the observed color excess of EB-V =0.68 (Forbes et al.,
1996) and the average efficiency of polarization for the interstellar
dust. The mean
angle of the polarization vectors of Hogg 22 is
θ=44o.9, which
agrees quite well with the expected angle produce by dust particles
aligned in the direction of the Galactic Plane
(θ=48o), while for NGC 6204 a lower value
θ=33o.7
was found. We believe that Hogg 22 is being depolarized by the
composition of the polarimetric vectors in front and behind of NGC 6204,
therefore a simple model of two different dust components with different
orientation of the magnetic field can explain the observations of Hogg
22.