What process following a spiral galaxy merger actively halts large-scale star formation in the resulting elliptical?

Answer

Supernovae feedback and AGN feedback heating or ejecting cold gas.

The intense starburst triggered by the collision generates supernovae and activates the central supermassive black hole (AGN feedback), which heats up or completely ejects the remaining cold gas, thus stopping star birth.

What process following a spiral galaxy merger actively halts large-scale star formation in the resulting elliptical?

#Videos

Differences Between Spiral And Elliptical Galaxies? - YouTube

galaxiesstar formationastrophysicselliptical galaxiesspiral galaxies