Galaxies die slowly as they use up the gas needed to form new stars
DOI: 10.1063/PT.5.028885
BBC : A massive comparison of dead and dying galaxies and active galaxies has provided clues to the late stages of galactic life. Yingjie Peng of the University of Cambridge and his colleagues combed through images collected by the Sloan Digital Sky Survey to examine 23 000 galaxies that are no longer producing stars and 4000 galaxies that are producing stars. In the unproductive galaxies, Peng’s team detected significantly more heavier metals than in the productive galaxies. If the galaxies had stopped producing new stars due to the sudden loss of gas clouds, the metal concentration would not have continued to grow. That suggests that the death process is drawn out over time. And the images showed that the active, star-forming galaxies were, on average, 4 billion years younger than the inactive galaxies.
