Um estudo polarimétrico na Região da Nuvem Molecular Lupus 1

Abstract

In this work, Hipparcos stars were measured at B-band in order to determine the distance to the molecular cloud Lupus 1. This catalogue contains distance measurements of stars with highly reliable values up to 150pc. The analysis of interestelar polarizationsuffered by this samples can provide a lower limit for the distance value to this cloud. These measurements, carried out with the IAG 60 cm telescope at Observatório do Pico dos Dias (LNA/MCT Braspolis MG), resulted in a distance estimate of 130-150 pc for the cloud. As an independent distance indicator, our values agree with the currently accepted values on the literature. Moreover, they confirm the existence of a void in the interestelar medium near to Lupus 1 and previously detected at 100 m by the IRAS satellite. In addition, this work contains the results obtained from polarimetric observations carried out in order to investigate the magnetic field geometry in the dark cloud Lupus 1 and near condensations. This study, based upon R-band CCD polarimetry, covers Lupus 1 and the surrounding area containing the 100 m IRAS cavity. A first analysis shows that the variation of the magnetic field orientation through the region can produce complex polarization patterns from which the field geometry cannot be easily determined. These patterns are inconsistent with a strictly uniform and unidimensional large scale magnetic field. But a comparison with the 100 m emission shows that, locally, the polarization vectors exhibit strong alignment with the orientation of some infrared patches detected by IRAS. For Lupus 1, the vectors measured are transverse to its filamentar structure, suggesting that its colapse may have occurred along the magnetic field lines.