Galaxies are broadly divided into star forming (gas rich) and quiescent (gas poor).
The mechanism responsible for shutting down star formation in galaxies and transforming
them into quiescent (“dead”) galaxies has been unclear so far.
Dr. Yingjie Peng and Prof. Roberto Maiolino have led a study published in Nature
in which they have analysed the stellar metallicities of thousands of nearby massive galaxies and
from which they have inferred that the main mechanism responsible for quenching star formation
in galaxies is “strangulation”, i.e. a process that halts the supply of gas to the galaxy.
For more information:
University press release: http://www.cam.ac.uk/research/news/cause-of-galactic-death-strangulation
Accompanying "News and views” in Nature: http://www.nature.com/nature/journal/v521/n7551/full/521164a.html
Nature paper: http://www.nature.com/nature/journal/v521/n7551/full/nature14439.html