Abstract
view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Luminosity Distribution of the Spiral Galaxy NGC 5055. Fish, Robert A. Abstract The luminosity distribution of XGC 5055 was studied with photographic photometry on the UB V system. On comparison of the luminosity distribution with the mass distribution found previously (Burbidge, E. M., Burbidge, G. K., and Prendergast, K. H. Astrophys. J. 131, 282, 1960), the mass-to-light ratios in each color are observed to rise at first, then decrease steadily on proceeding outwards from the nucleus. The over-all photographic M7L ratio for the galaxy out to 150" is 5.46. Three different indices of asymmetry are constructed from the photometric information. They reveal that the light distribution within 50" of the nucleus is inherently asymmetric, but that beyond 50" the three-dimensional light distribution is nearly axially symmetrical. Due to scattering and absorption of light the observed isophotes deviate widely from ellipses. If the albedo of the obscuring material is low, the intrinsic M7L ratios must vary only slowly from 50" outwards; if it is high the measured change of M7L by a factor of 5 between 50" and 150" represents very nearly the intrinsic change. The null effect of scattering on the average luminosity of NGC 5055 results from the inclination angle of the galaxy. If high scattering efficiency is a universal property of the obscuring matter in spiral galaxies, then very little light is degraded into the infrared, and photons entering the scattering layer are simply redirected toward normal emergence. Because of this redirection a face-on spiral must appear brighter and bluer than it would if no obscuring matter were present. The magnitude of this effect is evaluated by means of Holmberg's photometry (Lund Medd. Ser. II, No. 136, 1958); it is about 0.42 in total photographic brightness and 0.04 in color. The redirection of photons should be most prominent in the dusty regions of the face-on galaxy, creating an anomalous relative brightness and blueness of the spiral arms. Publication: The Astronomical Journal Pub Date: March 1961 DOI: 10.1086/108547 Bibcode: 1961AJ.....66R.283F full text sources ADS |
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