Distribution of the Intrinsic Shapes of Elliptical Galaxies

Abstract

We determine the distribution of the intrinsic shapes of the light distribution of elliptical galaxies by combining the profiles of photometric data from the literature with triaxial models. The models exhibit ellipticity variations and position angle twist. We use ensembles of models so that the shape estimates are largely model independent. We follow the methodology as described in Statler(1994) which is modified to suit our requirements. We find that short to long axial ratios at very small and at very large radii, and the absolute value of the triaxiality difference are the best constrained shape parameters. Using a flat prior, the shapes of elliptical galaxies are reported by Chakraborty et al.(2008). We now use a modified prior and therefore the shapes reported here are more reliable.Using modified prior, we have found the distribution of shape by analyzing twenty elliptical galaxies. We classify the ellipticals as flat or round depending upon the values of the short to long axial ratio. The plot shows the distribution of the number of galaxies as a function of (q0, q∞), where q0 and q∞ are the short to long axial ratios at small and at large radii. The number is shown in dark grey shade: darker is the shade larger is the number.