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Astron. Astrophys. 331, 737-741 (1998)

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5. Conclusions

In this paper we have presented the results of optical linear polarization measurements of stars in the region of the Puppis OB III association. It is found that the association members can be distinguished from the field stars on the basis of their polarization characteristics. The association members are characterized by a relatively large degree of polarization (average [FORMULA]) at position angles (in the galactic frame) around [FORMULA] compared with the low values (average [FORMULA]) of polarization at position angles around [FORMULA] for the field stars.

In the direction of Puppis OB III association there are two discrete regions of polarizing interstellar matter threaded by magnetic fields oriented quite differently. In a low density region, causing only small amount of polarization in field stars in the solar neighbourhood (within [FORMULA]) the field is oriented at large angles ([FORMULA]) to the Galactic plane, while a system of more dense clouds at a distance of [FORMULA] and probably related to the OB association itself, with the magnetic field more nearly parallel to the Galactic plane causes relatively larger polarization in the association member stars.

The ratio of polarization to reddening in the direction of the association is [FORMULA] times smaller than the mean interstellar value. This indicates either a very poor efficiency of dust grain alignment, or a magnetic field configuration that is predominantly longitudinal in this region.

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© European Southern Observatory (ESO) 1998

Online publication: February 16, 1998
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