Stellar kinematics is a fossil record of galaxy formation and evolution. In particular, the fraction of stars on near-circular orbits compared to
the fraction of stars on kinematically hotter and geometrically rounder orbits, speaks directly to the slowly accretion of gas flow or violent
merging/feedback of the galaxies’ past. On the other hand, stellar chemistry is conserved, thus a timing clock of a galaxy's formation. In
resolved system, like MW, the combination of stellar kinematics and stellar chemistry provide us unprecedented information to understand the formation of galactic structures. We developed a population-orbital model by tagging age and metallicities to the orbits in the Schwarzschild model, thus fitting the observed kinematics, age and metallicity maps simultaneously for external galaxies with IFU observation. The method is validated by testing against mock data, which show that it works well on recovering the intrinsic orbit distribution, intrinsic stellar population distribution and the correlations in between. We applied the method to FCC 167 with MUSE observations as a first case-study. Based on the model, we found a metal-rich thin disk, with a negative age gradient consistent to be grown inside-out, an old bulge with negative metallicity gradient consistent with the in-situ star formation with more metal-enrichment in the inner regions, and an inner halo component which is old and most metal-poor, consistent to be accreted from satellites. This is for the first time, an inner halo component is able to be decomposed from the integrated IFU data. The method can be widely applied to IFU surveys, making chemo-dynamical decomposition possible in unresolved systems, thus bringing the gap between external galaxies and MW.
