Another Flattened Dark Halo: Plar Ring Galaxy A0136-0801

Abstract

Knowledge of the shape of dark matter halos is critical to our understanding of galaxy formation, dynamics, and of the nature of dark matter itself. Polar ring galaxies (PRGs) --- early-type galaxies defined by their outer rings of gas, dust and stars on orbits nearly perpendicular to those of the central host --- provide a rare probe of the vertical-to-radial axis ratio $(q_{\rho} = c/a)$ of dark halos. We present a Fabry-Perot velocity field for the H$\alpha$ gas in the kinematically-confirmed PRG \gal. By comparing ring orbits evolved in a generalized mass model to the observed ring velocity field and morphology of \gal, we conclude that $q_\rho \sim 0.5$ and rule out a spherical geometry.Comment: uuencoded gz-compressed file with figures include