The Dark and Luminous Structure of NGC 3998
Nicholas Boardman
University of St Andrews
Anne-Marie Weijmans (University of St Andrews), Remco van den Bosch (Max Planck Institute for Astronomy), Ling Zhu (MPIA), Akin Yildirim (MPIA), Glenn van de Ven (MPIA), Michele Cappellari (University of Oxford)
We present integral-field spectra out to beyond 3 half-light radii for the lenticular galaxy NGC 3998, obtained with the Mitchell Spectrograph at McDonald Observatory, Texas. We extracted stellar kinematics for this galaxy, and we constructed dynamical models to investigate its dark and luminous structure. We obtain a stellar mass-to-light ratio in good agreement with independent stellar population modelling results for this system. We find our models to favour little dark matter within the central half-light radius and to support a near-isothermal total density profile. We obtain tight constraints on the galaxy viewing angle as a result of our wide field of view, finding NGC 3998 to be flattened and near-axisymmetric. We find that the galaxy becomes increasingly disc-dominated in the outskirts, with few radial orbits beyond the central effective radius. We conclude by discussing how our models may be used to constrain this galaxy’s evolutionary history