Quenched massive spiral galaxies have attracted great attention recently, as more data is available to constrain their environment and cold gas content. However, the quenching mechanism is still uncertain, as it depends on the mass range and baryon budget of the galaxy. In this talk, we report the identification of a rare population of very massive, quenched spiral galaxies with stellar mass ≳10^11 M⊙ and halo mass ≳10^13 M⊙ from the Sloan Digital Sky Survey at redshift z∼0.1. Our CO observations using the IRAM-30m telescope show that these galaxies contain only a small amount of molecular gas. Similar galaxies are also seen in the state-of-the-art semi-analytical models and hydro-dynamical simulations. It is found from these theoretical models that these quenched spiral galaxies harbor massive black holes, suggesting that feedback from the central black holes has quenched these spiral galaxies. This quenching mechanism seems to challenge the popular scenario of the co-evolution between massive black holes and massive bulges.

Prof. Xi Kang is the director of the joint astronomy center between ZJU and Purple Mountain Observatory, CAS. He got his PhD at Shanghai Astronomical Observatory in 2005, and worked as a postdoc at the university of Oxford, Max-Planck-Institute for Astronomy, from 2005-2009. From 2009-2019, He was leading the galaxy and cosmology group at PMO. From end of 2019, he moved to Zhejiang University and is now involving the buildup of astrophysics in ZJU.

His main research interest focus on galaxy formation and the large-scale structure. In recent years he has been working on galaxy alignment on different scales, using both N-body simulations and the observational data. In particular, he and his collaborator proposed the two-stage scenario to explain the correlation between galaxy spin and cosmic filament. He is also coordinating and partly leading the NIHAO project.