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 on the CALIFA galaxies.

BIO
Prof. Ling Zhu is a faculty member in Shanghai Observatory since 09/2018. Prior to this, She were a posdoc at the Max Planck institute for Astronomy (Heidelberg, Germany) working with Glenn van de Ven from 09/2013-08/2018. She got her PhD degree at the center for Astrophysics, Tsinghua University, under the supervision of Shude Mao. She obtained her bachelor degree also from Tsinghua University, Beijing (2008, department of physics).

Host: Prof. Dandan Xu