CCA Colloquium: Ke Zhang

Title: Gas Evolution in Protoplanetary Disks

Abstract: Protoplanetary disks are cradles of planet formation. These disks play a vital role in shaping fundamental properties of planetary systems, such as the number of rocky and giant planets, as well as the bulk compositions of planetary cores and primordial planetary atmospheres. Gas is the dominant mass constituent in protoplanetary disks, taking 99% of mass initially. Yet, it is still unclear how the gas mass evolves and what mechanism drives its evolution, which has become a major challenge in understanding planet formation processes. In this talk, I will discuss results from the ALMA survey of Gas Evolution in PROtoplanetary disk, AGE-PRO, an ALMA Cycle 8 large program. We collected deep ALMA observations of a comprehensive sample of 30 disks throughout the typical disk lifetime. By combining AGE-PRO observations and state-of-the-art thermo-chemical models, we provide accurate gas mass and size measurements of these disks. I will discuss how our results are compared with predictions from two leading theories of disk evolution: Turbulent viscosity and Magneto-hydrodynamical disk winds. Finally, I will show the JWST MIRI observations of the same sample, which provides important insight into the chemical evolution in the inner few au region.