Examination of azimuthally-averaged surface brightness profiles of the spiral arms using decomposition.

Abstract

For the first time we perform the decomposition of 29 galaxies from S4G survey considering spiral arms as a separate component. We analyze the contribution of spiral arms to the azimuthally-averaged profiles of galaxies’ surface brightness using our models, using models obtained with decomposition. We show that spiral arms’ contribution varies strongly with distance to the center, usually reaching its highest value at the radius of about 1,5 exponential scale of the disk and decreasing to zero at the center and on the periphery of the galaxy. We obtain the characteristic values of the «bump» height on the galaxy’s azimuthally-averaged profile which is caused by the spiral arms. Spiral arms’ contribution to the overall luminosity of the galaxy is investigated, its connection with the Hubble type is also confirmed. Our results can be applied, for the rough estimates of axisymmetric components’ share in galaxy’s light, which is important for determination of disk parameters based on azimuthally-averaged surface brightness profiles, or for analysis of the spectral energy distribution in galaxy.