(ORDO NEWS) — In the first few billion years after the Big Bang, there were many more so-called stellar galaxies in the universe than models predict. Between 60 and 90% of the stars in the early universe appear to have been spawned by galaxies undergoing a growth spurt.
This was shown by an analysis of more than 20,000 distant galaxies. The team, led by astronomers from the University of Groningen in the Netherlands, will soon publish their findings in The Astrophysical Journal.
Star galaxies are galaxies that are in the growth stage. They produce many more stars than usual in a relatively short period of time. Stellar growth lasts from 10 to 100 million years. Galaxies often live for billions of years and may experience several growth spurts.
A sudden influx of gas is needed to trigger a growth spurt, otherwise the building blocks for new stars will soon run out. Such an influx can occur, for example, when two galaxies approach each other.
A research team led by Pierluigi Rinaldi, a doctoral student at the University of Groningen (Netherlands), studied data on more than 20,000 distant galaxies.
This data has been collected in recent years by the Hubble Space Telescope, the MUSE instrument at the European Very Large Telescope in Chile, and the Spitzer Space Telescope.
Telescopes have looked so far into the past that researchers have been able to study galaxies that formed 11 to 13 billion years ago. The Big Bang happened 13.7 billion years ago.
The analysis shows that in the first few billion years after the Big Bang, 20 to 40% of all star-forming galaxies were stellar galaxies.
During the period of growth, these galaxies accounted for 60 to 90% of the new growth of stars. In comparison, today the Universe is much calmer, and only about 10% of new stars are born in stellar galaxies.
Moreover, the analysis shows that growth spurts occur more often in small galaxies than in large ones. It turns out that many small flare galaxies came into the field of view of telescopes at the very moment of their formation. “In that sense, you can compare it to the growth spurt in humans. It’s also strongest in infancy,” says Rinaldi.
The results came as a surprise because, until recently, flare galaxies were thought to be uncommon and of little importance in galaxy formation and growth.
“Even the most recent and sophisticated models of galaxy formation did not predict this,” says Rinaldi. “It seems likely that physical processes occur on a scale too small for models to account for.”
Karina Kaputi (University of Groningen), Rinaldi’s supervisor, adds: “Of course, this gives us reason to think about these models. And this is a good sign.
In the coming period, Kaputi wants to continue studying the origin and evolution of the first galaxies. It can do so because it recently received an NWO Vici grant, and because the James Webb Space Telescope will also point its mirrors at distant galaxies.
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