Dissecting discs and bulges with SAMI and Romulus

Integral field surveys like SAMI are providing spatially-resolved kinematics for thousands of disc galaxies, while cosmological simulations like Romulus resolve galaxy formation on similar scales. However, little progress has been made on methods to measure structural properties - a key to exploiting these rich new datasets. We have developed a new method to fit self-consistent 3D bulge+disc+halo models to multi-wavelength data using Bayesian (MCMC) routines. I will show that our code can simultaneously reproduce deep imaging, SAMI kinematics and unresolved 21cm HI emission of regular spirals, measuring fundamental properties like mass, size and spin with more robust uncertainties than traditional 2D methods. I will also present predictions for disc galaxy scaling relations from the new high-resolution Romulus cosmological simulation, using novel, realistic SAMI-equivalent synthetic observations. Finally, I will outline how these methods will soon converge to a comprehensive picture of disc galaxy evolution from z=1 to today.