Stellar population synthesis with distinct kinematics: Multiage asymmetric drift in SDSS-IV MaNGA galaxies

We present the first asymmetric drift (AD) measurements for unresolved stellar populations of different characteristic ages above and below 1.5 Gyr. These measurements sample the age-velocity relation in galaxy disks. In this first paper, we develop two efficient algorithms to extract AD on a spaxel-by-spaxel basis from optical integral-field spectroscopic data cubes. The algorithms apply different spectral templates, one using simple stellar populations and the other a stellar library; their comparison allows us to assess systematic errors in derived multicomponent velocities, such as template mismatch. We test algorithm reliability using mock spectra and Monte Carlo Markov Chains on real data from the MaNGA survey in Sloan Digital Sky Survey IV. We quantify random and systematic errors in AD as a function of signal-to-noise and stellar population properties with the aim of applying this technique to large subsets of the MaNGA galaxy sample. As a demonstration of our methods, we apply them to an initial sample of seven galaxies with comparable stellar mass and color to the Milky Way. We find a wide range of distinct AD radial profiles for young and old stellar populations.