Photoelectric Measurements of Polarization in the Irregular Galaxy M82, NGC 5128, the Pleiades and Other Objects.

Abstract

view Abstract Citations (5) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photoelectric Measurements of Polarization in the Irregular Galaxy M82, NGC 5128, the Pleiades and Other Objects. Elvius, Aina ; Hall, John S. Abstract Photoelectric observations were made with a dc polarimeter attached to the 69-inch Perkins Reflector of Ohio Wesleyan University and the Ohio State University at the Lowell Observatory at its new site near Flagstaff. Circular apertures of 27" and 40" were usually used. The main survey was made in integrated light. Some of the highly polarized regions were later studied in blue and yellow light. M82 was studied thoroughly. Its brightest spot shows very little polarization. Other parts of the main body show 2-3 % with the electric vector parallel to the main axis of the object in general agreement with three measures in the central areas by Dombrovsky (Astron. Circ. U.S.S.R. No. 176,1956). In the outer faint filaments the polarization is as high as 15 %. The electric vectors are perpendicular to the filaments, indicating that the filamentary structure is associated with a magnetic field, similar to a dipole field. The AS spectrum and red color of M82 suggest vast clouds of solid particles. Its seems reasonable to assume that the same particles scatter light from the bright inner parts which also contain hot emission regions. Elongated grains oriented in the magnetic field would explain the observations as suggested by A. Elvius (Uppsala Astron. Obs. Medd. No. 121, 1959). The flat radio spectrum of M82, observed by Lynds (Astrophys. 1. 134, 659, 1961) may be caused by thermal radiation from the H ii regions, or by synchrotron radiation. Both processes could contribute to the observed polarization. Five percent polarization has also been detected in NGC 5128 (Centaurus A). Observations of 10 other galaxies gave no strong evidence of polarization. Extensive observations have been made of nebulosity in the Pleiades. Polarization as large as 10% was detected in some areas showing filamentary structure. The reductions are complicated by the polarization of regions within the cluster which are apparently free of filamentary structure. Publication: The Astronomical Journal Pub Date: 1962 DOI: 10.1086/108648 Bibcode: 1962AJ.....67R.271E full text sources ADS |