Observations indicate that massive elliptical galaxies in the contemporary universe exhibit both low star formation rates and low AGN luminosity. This raises a question: Given continuous gas accretion, how do these massive ellipticals maintain their quiescent state? SMBH feedback is a widely accepted solution to this issue, yet the mechanisms how it prevents gas accretion and subsequent star formation remain debated. In this talk, I will present our recent simulation studies on this issue. Our simulations, conducted under the MACER project—a 2D radiation hydrodynamical simulation suite for idealized massive ellipticals—now include a novel extension that incorporates external gas inflow. This modification has allowed us to explore the impacts and fate of such inflows within the original MACER suite. Our findings reveal that most of the cosmological inflow become the part of circumgalactic medium (CGM) and do not significantly influence the late-stage evolution of massive ellipticals. Further investigations confirm that the quiescent state of these galaxies are sustained by AGN feedback, but through explosive quasar winds rather than radio feedback in MACER galaxies.
