In one of the first astrophysical studies of the “cosmic dawn” (the period that includes the beginning of Universewhen the first stars appeared), an international team of researchers has obtained important information about The first galaxies that formed.
Using data from India’s SARAS 3 radio telescope, astronomers led by the University of Cambridge in the United Kingdom have been able to observe the very young universe – just 200 million years after the great explosion – Determine the limits of mass and energy resulting from the first stars and galaxies.
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They did this while searching for the signal known as the “21 cm hydrogen line”, which was not detected. This non-discovery allowed the scientists to make further determinations about the period, allowing them to rule out certain scenarios, such as galaxies that were inefficient heaters of cosmic gas and effective producers of radio emissions.
Although we still haven’t been able to directly observe these first galaxies, the results described in an article published Monday (28) in the journal natural astronomyIt represents an important step in understanding how our universe went from being practically empty to star-filled space.
According to the site phys.orgThe project range of square kilometres (SKA) — which includes two next-generation telescopes due for completion by the end of this decade — will likely be able to image the early universe, but for current telescopes, the challenge is detecting the cosmic signal from the first stars radiated by dense clouds of light and hydrogen. .
It is this signal that is called the 21 cm line – a radio callsign produced by hydrogen atoms. Analyzes made using radio telescopes such as Radio experiment to analyze cosmic hydrogen REACH can tell us about entire groups of older galaxies. The first REACH results are expected in early 2023.
Earlier this year, the authors of this latest study developed a method that they say will allow them to see through the haze of the early universe and detect the light of the first stars. Some of these techniques have already been put into practice in the current research.
In 2018, another research group, which runs the EDGES experiment, published a paper proposing a possible discovery of this ancient light. The reported signal was unusually strong compared to what would be expected in the simplest astrophysical picture of the early universe. However, SARAS 3 data disputed this finding, and the EDGES result remains to be confirmed by independent observations.
In this latter approach, the Cambridge-led team tested a variety of astrophysical scenarios that could explain the EDGES result, but found no corresponding signal.
Working with collaborators in India, Australia and Israel, the team used statistical modeling techniques to detect the signal in the SARAS 3 data. “We were looking for a signal of a certain amplitude,” said Harry Bivins, a doctoral student in the Cavendish Lab. from Cambridge, and lead author of the paper. “But by not finding this signal, we were able to put a limit on its depth. This, in turn, begins to tell us how bright the first galaxies were.”
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Groundbreaking in many respects, this observational study rules out scenarios in which the first galaxies were a thousand times brighter than current galaxies in the narrow band emission. radio Hydrogen gas heaters were poor.
“Our data also reveals something that has been suggested before, that the first stars and galaxies could have made a measurable contribution to the background radiation that appeared as a result of the Big Bang and has been traveling toward us ever since,” said Eloy D. Lyra Acedo, a Cavendish Laboratory scientist who co-led the research.
“It’s amazing to be able to look so far back in time — to just 200 million years after the Big Bang — and to be able to learn about the early universe,” Bivins said.
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