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Starburst galaxies flourished in the early universe

A red-green spot (a starburst galaxy).
An example of an active star-forming galaxy – also known as one of the starburst galaxies (in green and red) – in the early distant Universe. This galaxy’s nickname is Baby Boom. It is about 12.3 billion light years away. The galaxy produces an average of 4,000 stars per year, more than 10 times the number produced by our own Milky Way. Image via Spitzer/NOVA.

An abundance of starburst galaxies

The Netherlands Research School for Astronomy (NOVA) said this morning (4 April 2022) that a new analysis of more than 20,000 distant galaxies has revealed an unexpected abundance of starburst galaxies in the early Universe. Starburst galaxies have an exceptionally high rate of star formation, about 10 times or more higher than in ordinary galaxies like our Milky Way. These astronomers said that in the first few billion years after the Big Bang, the Universe contained far more starburst galaxies than theoretical models predict. They said that when the Universe was only a few billion years old (as opposed to 13 billion years now) – starburst galaxies produced 60-90% of the stars.

So the early universe was a hotbed of star formation!

Astronomers from the University of Groningen (Netherlands) led this new research, which will soon be published in the peer-reviewed journal Astrophysical Journal (Preprint at arXiv).

Studying galaxies 11 to 13 billion years ago

Pierluigi Rinaldi from the University of Groningen (Netherlands) led the research team. The team examined observational data from more than 20,000 distant galaxies. These astronomers used data collected in recent years with the Hubble Space Telescope, with the MUSE instrument on the European Very Large Telescope in Chile, and with the Spitzer Space Telescope. Her statement stated:

The telescopes looked so far into the past that researchers were able to study galaxies that formed 11 to 13 billion years ago. The Big Bang was 13.7 billion years ago.

Rinaldi commented:

In that sense, it can be compared to the human growth spurt. This is also strongest in infancy.

A happy looking young man standing next to a Dutch canal lined with old houses.
Astronomer Pierluigi Rinaldi, a Ph.D. Student at the University of Groningen, led the new research on starburst galaxies. Image via LinkedIn.

galaxies in growth spurt

The NOVA statement states:

Starburst galaxies are galaxies in a growth spurt. And they produce many more stars than normal in a relatively short period of time. A stellar growth spurt lasts 10 to 100 million years. Galaxies often live for billions of years and can go through multiple growth spurts. To trigger a growth spurt it needs a sudden influx of gas, otherwise the building blocks for new stars will soon run out. Such an influx can occur, for example, when two galaxies approach each other…

Analysis shows that in the first few billion years after the Big Bang, about 20-40% of all star-forming galaxies were starburst galaxies. These galaxies in a growth spurt accounted for 60-90% of the new star growth.

By comparison, the universe is much quieter today, and only about 10 percent of new stars are born in starburst galaxies.

Young woman with a Mona Lisa smile and red hair.
Karina Caputi from the University of Groningen is Pierluigi Rinaldi’s supervisor. Image via Karina Caputi.

Realizing the importance of starburst galaxies

Until recently, starburst galaxies were considered uncommon and of minor importance in galaxy formation and growth. Rinaldi commented:

Even the newest and most sophisticated models of galaxy formation had not predicted this. It seems likely that the physical processes are occurring on too small a scale for the models to account for.

Karina Caputi (University of Groningen), supervisor of Rinaldi, added:

Of course, this gives us food for thought with regard to these models. And that’s a good sign.

Caputi added that she wants to continue studying the origin and evolution of the first galaxies.

Pie charts in blue and red for different numbers of starburst galaxies over time.
View larger. | Illustration showing different rates of star formation between ordinary (main sequence) galaxies like our Milky Way and active star-forming galaxies, so-called starburst galaxies. Image via Astronomie.nl.

Conclusion: The early Universe was a hotbed of star formation. In the first few billion years, our universe appears to have produced 60-90% of its stars in starburst galaxies. These galaxies produce stars ten times or faster than the ordinary galaxies we see in space around us today.

Source: The galaxy’s starburst/main sequence bimodality over five decades in stellar mass at z~3-6.5

About Astronomie.nl

https://earthsky.org/space/starburst-galaxies-flourished-in-the-early-universe/ Starburst galaxies flourished in the early universe

Tom Vazquez

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