Early universe was lit up by gas-rich baby galaxies

James Webb Space Telescope (JWST) images show that almost 90% of the galaxies in the early universe were abundant in brightly glowing gas that outshone emerging stars.

The study is published in the Astrophysical Journal.

The “extreme emission line features” in the 12-billion-year-old galaxies were studied by an international team of astronomers led by Australian researchers.

“The stars in these young galaxies were remarkable, producing just the right amount of radiation to excite the surrounding gas,” says lead author Dr Anshu Gupta from the ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D). “This gas, in turn, shone even brighter than the stars themselves.”

Gupta is also from the Western Australian Curtin University node of the International Centre for Radio Astronomy Research (ICRAR).

“Until now, it was challenging to understand how these galaxies were able to accumulate so much gas. Our findings suggest that each of these galaxies had at least one close neighbouring galaxy. The interaction between these galaxies would cause gas to cool and trigger an intense episode of star formation, resulting in this extreme emission feature.”

The study was built on data obtained as part of the JWST Advanced Deep Extragalactic Survey (JADES).

Gupta says the findings were made possible by the JWST’s ability to peer into the early universe at resolutions never seen before.

“With this detail we were able to see a marked difference in the number of neighbours between galaxies with the extreme emission features and those without. Prior to JWST, we could only really get a picture of really massive galaxies, most of which are in really dense clusters making them harder to study.”

“We suspected that these extreme galaxies are signposts of intense interactions in the early universe, but only with the sharp eyes of JWST could we confirm our hunch,” says co-author Associate Director Kim-Vy Tran, also from the ASTRO 3D as well as the Harvard and Smithsonian Center of Astrophysics.

The authors say that their results will not only illuminate what the early universe looked like, but also how galaxies such as our own formed later on.

“What’s really exciting about this piece is that we see emission line similarities between the very first galaxies to galaxies that formed more recently and are easier to measure. This means we now have more ways to answer questions about the early universe, a period that is technically very hard to study,” says second author Ravi Jaiswar, a PhD student at Curtin University.

“By understanding what early galaxies look like, we can build on answering questions on the origin of the elements that make up our everything in our everyday life here on Earth,” says ASTRO 3D director Professor Emma Ryan-Weber, who was not directly involved in the study.

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