New images of galaxies reveal an irregular beginning of the Universe


SHARDS study image.
UNIVERSITY OF NOTTINGHAM

An international team of astronomers from the University of Nottingham and the Center for Astrobiology (CAB, CSIC-INTA) used data from the Hubble Space Telescope (HST) and the Gran Telescopio Canarias (GTC), the so-called Frontier Fields, to locate and study some of the smallest galaxies in the nearby universe. This has revealed that galaxy formation is likely to be irregular. The first results have just been published in the magazine Monthly Notices of the Royal Astronomical Society (MNRAS).

One of the most interesting questions astronomers have been trying to answer for decades is how and when the first galaxies formed. As for how, one possibility is that the formation of the first stars within galaxies began at a steady rate, slowly building an increasingly massive system. Another possibility is that the formation was more violent and discontinuous, within tension, but short-lived star formation bursts triggered by events such as mergers and increased gas accumulation.

“The formation of galaxies can be compared to a car,” explains Pablo G. Pérez-González, one of the co-authors of the article, affiliated with the Astrobiology Center (CAB / CSIC-INTA), and principal investigator of the international collaboration behind this study. “The first galaxies could have had a ‘diesel’ star formation engine, adding new stars slowly but continuously, without much acceleration and gently converting the gas into relatively small stars over long periods of time. Or the formation could have been uneven, with bursts of star formation that produce incredibly large stars that disturb the galaxy and cause it to cease its activity for a time or even forever. Each scenario is linked to different processes, such as galaxy mergers or the influence of supermassive black holes, and they have an effect on when and how carbon or oxygen was formed, which are essential for our life. ”

Using the power of gravitational lens of some of the most massive galaxy clusters in the Universe with the exceptional GTC data from a project titled Survey for high-z Red and Dead Sources (SHARDS), astronomers looked for close analogues of the first galaxies formed in the Universe, so that they could be studied in much more detail.

Dr. Alex Griffiths of the University of Nottingham was one of the lead researchers on the study in the UK, he explains: “Until we have the new James Webb Space Telescope, we won’t be able to observe the first galaxies to form, they are just too faint. We look for similar beasts in the nearby Universe. and we dissect them with the most powerful telescopes we currently have. ”

Use of “natural telescopes”

The researchers combined the power of the most advanced telescopes, such as HST and GTC, with the help of “natural telescopes.” Professor Chris Conselice of the Manchester University is a co-author of the study, said in a statement: “Some galaxies live in large groups, what we call clusters, which contain enormous amounts of mass in the form of stars, but also gas and dark matter. Their mass is so great that they double space. -time, and they act like natural telescopes. We call them gravitational lenses and they allow us to see faint and distant galaxies with higher brightness and higher spatial resolution. ”

Observations of some of these massive clusters that act as gravitational telescopes are the basis of the Frontier Field study. The study showed that galaxy formation was likely to stop and begin with bursts of activity followed by pauses.

Dr Griffiths from the University of Nottingham said: “Our main finding is that the onset of galaxy formation is intermittent, like a jerking car engine, with periods of enhanced star formation followed by intervals of sleep. It is unlikely. that galaxy mergers have played a “substantial role in triggering these star-forming bursts and is most likely due to alternative causes that enhance the gas accumulation, we need to look for those alternatives.

“We were able to find these objects thanks to the high-quality SHARDS data along with the image data from the Hubble Space Telescope to detect hot gas heated by newly formed stars in very small galaxies. This hot gas emits at certain wavelengths, what we call emission lines, as a neon light. Analysis of these emission lines can provide insight into the formation and evolution of a galaxy. ”

“The SHARDS Frontier Fields observations made with GTC have provided the deepest data ever taken to discover dwarf galaxies through their emission lines, allowing us to identify systems with star formation recently unleashed, “adds Pérez-González, one of the co-authors of the paper and principal investigator of the GTC SHARDS Frontier Fields project.

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