"Quiescent galaxies" refers to galaxies that are not actively forming new stars and are relatively calm or inactive in terms of their star formation activity. Full definition
When black holes stop eating, quasars can turn off, becoming quiescent galaxies. (newscientist.com)
For galaxies less than twice as massive as the Milky Way — the vast majority — star - forming galaxies possess less iron and other heavy elements than quiescent galaxies of the same mass. (sciencemag.org)
With the help of the Hubble Space Telescope's recently enhanced vision, researchers have uncovered flickers of star formation in these quiescent galaxies. (discovermagazine.com)