Galaxies Are Strangled for 4 Billion Years Until They Die
An interesting study claims to have solved the mystery of galactic death at least partly, when it zeroed on strangulation as the cause of death.
It is know that galactic death can occur when a galaxy runs out of its store of star-forming fuel - Hydrogen. Hydrogen could be exhausted either abruptly when all of it is sucked out from the galaxy or the supply of it into the galaxy could reduce until it stops, resulting in galactic death akin to strangulation.
Additionally, researchers knew that metal levels in a galaxy increase as star creation increases. Also, metal levels in galaxies that die abruptly do not change after death. However, the levels increase in galaxies that die a slow death.
Using the Sloan Digital Sky Survey, researchers analyzed metal levels in more than 26,000 average-sized galaxies located in the Milky Way area of the universe. They then compared metal levels between live and dead galaxies only to find a massive difference.
"We found that for a given stellar mass, the metal content of a dead galaxy is significantly higher than a star-forming galaxy of similar mass," said Professor Roberto Maiolino, co-author of the new study.
"Metals are a powerful tracer of the history of star formation: the more stars that are formed by a galaxy, the more metal content you'll see. So looking at levels of metals in dead galaxies should be able to tell us how they died," said Dr. Yingjie Peng the paper's lead author.
Researchers then determined the average age difference between the dead and live galaxies to arrive at four billion years, which is the amount of time it takes a star-forming galaxy to be strangled to death.
