Other
Scientific paper
Aug 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003basbr..23..222p&link_type=abstract
Boletim da Sociedade Astronômica Brasileira (ISSN 0101-3440), vol.23, no.1, p. 222-223
Other
Scientific paper
We present linear polarization measurements of the Bok Globules DC301.4-7.9, DC301.5-7.7, DC301.7-6.7 and B68 in optical (R) and infrared (H) bands. The observations were made using the IAGPOL polarimeter at the f/13.5 Cassegrain focus of the 0.6m IAG Telescope at the Observatório do Pico dos Dias/Laboratório Nacional de Astrofísica, Brasil. The first element in the beam is a rotatable, achromatic half-wave retarder followed by a Savart plate as analyzer. The retarder is conveniently selected to match the band used. The analyzer provides two images of each object in the field with orthogonal polarizations. One polarization modulation cycle is covered for every 90" rotation of the waveplate. The simultaneous imaging of the two beams allows observing under nonphotometric conditions and at the same time the sky polarization is practically canceled. The Bok globules studied could be associated to a disruption of the near filamentary Musca Dark Cloud (~ 200-250 pc). It is important to know if the local magnetic field is perturbed in the environments of the globules and if correlations between the magnetic field structure and their morphology are present. In general, optical polarimetry shows the magnetic field at the periphery of the globules where the extinction is not as high. In other hand, infrared polarimetry is able to analyze the more interior regions and correlations with the optical data could be done. In this study, for some of the globules we detect a significant amount of optical polarization (higher than 2%) for the background stars. The polarization maps are shown. In general, a very homogeneous magnetic field pattern is inferred, although a smooth, twisted pattern also is evident in some cases. We also use the dispersion of the polarization position angles to estimate the magnetic field in the regions. This work is supported by FAPESP. AMM is partly supported by CNPq.
Magalhaes Antonio Mario
Pereyra Antonio
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