Predicting line-of-sight velocity distributions of elliptical galaxies

Abstract

We extend the galaxy modelling technique of Binney, Davies & Illingworth to the calculation of the predicted line-of-sight velocity distribution (LOSVD) at each point on the sky. Following Gerhard and van der Marel & Franx we characterize the LOSVD by the coefficients hj in its optimized Gauss-Hermite expansion. We prove some results concerning this expansion and test our technique on pseudo-data. We find that LOSVDs, under the assumption of velocity dispersion isotropy, can be accurately predicted out to two effective radii provided that the galaxy has inclination angle i≳70°.