Disentangling galaxy formation history through a population-orbit superposition model

Stellar kinematics is a fossil record of galaxy formation and evolution. In particular, the fraction of stars on approximately circular and co-planar 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, stars conserve chemical properties since their birth, chemistry is a widely-used indication of stellar age. The combination of stellar kinematics and stellar chemical age may provide us unprecedented information to understand the formation of galactic structures.  The IFU surveys, like CALIFA and MaNGA, provide us information integrated along the line-of-sight, including the surface brightness, kinematic maps, mean age and metallicity maps from stellar-population synthesis of the spectra across the 2D sky-plane.Using the orbit-superpostion Schwarzschild method, we have been able to derive the internal stellar orbit distribution for a sample of 300 CALIFA galaxies, which form an orbit-based ‘dynamical Hubble sequence’.Decomposition of different orbital structures is thus possible based on the orbit distribution. In order to obtain chemical information of these orbital structures, we further develop a population-orbit superposition model, by tagging age and metallicities to the orbits in the Schwarzschild model. This is an on-going work, I will show you various method-tests and some preliminary results of application to MUSE observed galaxies. 

Prof. Ling Zhu
KIAA 1st meeting room
Wed, 2019-03-27 12:00 to 13:00