Photoelectric Three-color Observations of Polarization in the Light from the Reflection Nebulae NGC 2068, 7023 and IC 349, the Crab Nebula and the Galaxies NGC 1068, 3034 and 7814.

Abstract

view Abstract Citations (6) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photoelectric Three-color Observations of Polarization in the Light from the Reflection Nebulae NGC 2068, 7023 and IC 349, the Crab Nebula and the Galaxies NGC 1068, 3034 and 7814. Elvius, A. ; Hall, J. S. Abstract The observations were obtained with the 69-in. Perkins reflector of Ohio Wesleyan and the Ohio State University at the Lowell Observatory during the fall of 1964. A GlanFoucault prism was used as analyzer in the polarimeter, and all measures were made with color filters centered in the uv, blue, and yellow spectral regions. (a) Reflection Nebulae: Measurements have been made in several points in NGC 2068, NGC 7023 and -the Merope Nebula (IC349). The degree of polari;zation was found to be higher in yellow light than in the shorter wavelengths, as previously mentioned by Gehrels. The degree of polarization, however was usually not found to be a linear function of 1/A, and the slope seems to increase with increasing angular -distance from the illuminating star. Though the direction of polarization is in many cases related to the direction to the illuminating star, it was sometimes found to be clearly related to the direction of nebular filaments. (b) Crab Nebula: Observations indicate that the polarization is nearly the same in all three colors, as expected from the theory of synchrotron radiation. (c) Galaxies: Some faint regions of M82, containing filaments, have been observed. Although photographs published by Sandage (Science 144, 407, 1964) indicate a very high polarization in these regions, the photoelectric data so far reduced show no more than 25 % polarization in any of the three colors. Polarization has been observed in NGC 1068 where Walker has already reported high uv polarization in its nucleus (Astron. J. 69, 682, 1964). The degree of polarization decreases with wavelength, probably because of the mixture of synchrotron radiation with unpolarized starlight. Polarization was also found in the dark lane crossing over the central part of NGC 7814. The electric vector is generally parallel to the dark lane and the polarization is probably due to absorption. Publication: The Astronomical Journal Pub Date: 1965 DOI: 10.1086/109579 Bibcode: 1965AJ.....70R.138E full text sources ADS |