Astronomers have found a link between starbursts in the early Universe and the most massive galaxies found today.
The international team – including researchers from the University of Durham – combined observations from the LABOCA camera on the ESO-operated Atacama Pathfinder Experiment (APEX), the Very Large Telescope, NASA’s Spitzer Space telescope and others to look at how bright, distant galaxies are clustered together.
The galaxies are so distant that their light takes around ten billion years to reach us – so the astronomers are seeing the galaxies as they were ten billion years ago. In their images of the early Universe, the galaxies are undergoing starburst – the most intense type of star formation.
The closer these galaxies are clustered, the more massive their halos of dark matter. By measuring the dark matter halo around galaxies, and using computer simulations to study their growth, the team found these starburst galaxies eventually become giant elliptical galaxies – the most massive in today’s Universe.
“This is the first time that we’ve been able to show this clear link between the most energetic starbursting galaxies in the Universe, and the most massive in the present day,” said lead scientists Ryan Hickox.
Observations show that bright starbursts in these galaxies last for 100 million years – which is short in cosmological terms – but during this time, they are able to double the quantity of stars in the galaxy.
“We know that massive elliptical galaxies stopped producing stars rather suddenly a long time ago and are now passive,” said Julie Wardlow. “Scientists are wondering what could possibly be powerful enough to shut down an entire galaxy’s starburst.”
Astronomers believe the culprit may be the emergence of supermassive black holes. Starburst galaxies cluster in a similar way to quasars – indicating that they are found in the same dark matter halos. Evidence suggests that the intense starburst powers the quasar by feeding enormous quantities of material into the black hole. The quasar in turn emits powerful bursts of energy that are believed to blow away the galaxy’s remaining gas – the raw material for new stars – and shuts down the formation phase.
“In short, galaxies’ glory days of intense star formation also doom them by feeding the giant black hole at their centre, which then rapidly blows away or destroys the star-forming clouds,” said David Alexander from the department of physics at Durham.