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Unusual clouds of glowing gas discovered around super distant galaxies

A team of CATA astronomers was able to see these “green clouds” of ionized oxygen with the James Webb Space Telescope in a group of galaxies whose light came out when the Universe was only 10% of its present age.

One of the positive aspects of the development of astronomical instrumentation in recent years is that it has made it possible to overcome certain frontiers of study that seemed inaccessible until recently, as in the case of very distant galaxies.

Thanks to the information obtained with the James Webb Space Telescope (JWST), a team of researchers from the Center for Astrophysics and Related Technologies, CATA, detected two gigantic nebulae of ionized oxygen at the periphery of a group of distant galaxies. According to the researchers’ analysis, these clouds-which are as large as a galaxy-shine with a characteristic green color when illuminated by an active galactic nucleus (AGN). AGNs are extremely energetic events associated with the growth of the supermassive black hole at the center of galaxies.

This “green cloud” phenomenon has also been observed in the nearby Universe. There is an object known as Hanny’s Voorwerp that shares several characteristics with the clouds discovered with the JWST and has been interpreted as the echo of light from an AGN that would have been extinguished in a nearby galaxy.

CATA astronomer Manuel Solimano (PhD student at Universidad Diego Portales), working together with Manuel Aravena (CATA Associate Researcher and academic at Universidad Diego Portales) and Jorge González-López (CATA Assistant Researcher and academic at Universidad Católica), were able to detect these clouds in the group of galaxies J1000+0234, located at such a distance that it has a redshift of 4. 5 (this means that their light was emitted 12.4 billion years ago, when the Universe was 10% of its present age). This group is part of a region that harbors numerous galaxies classified as a “proto-cluster of galaxies”. That is, this structure will probably evolve into a cluster of galaxies like those we see in the nearby Universe.

This study was reported in the article entitled “A hidden active galactic nucleus powering bright nebulae in a protocluster at z = 4.5 revealed by JWST” published in the prestigious journal Astronomy & Astrophysics.

This discovery is significant because it provides evidence that AGNs can be present in early stages of structure formation in the Universe, even though they are highly obscured. The energy of these AGNs can affect their environment in important ways, driving processes such as star formation or large-scale gas distribution in proto-clusters. Furthermore, the detection of these hidden AGNs could change the way we understand the co-evolution of galaxies and black holes.

“The first thing we were able to determine is that these types of objects did exist at these distances, at early times, and that we observed them without looking for them also tells us that they may be much more common than one would expect. A supermassive black hole is bound to affect what’s going on in a galaxy, we know that. But here we’re seeing it affect the gas beyond the galaxy, in the circum-galactic medium. We have a case where a supermassive black hole is ionizing gas on a very large scale”, explains Jorge González López.

One of the striking aspects of this finding is that the AGN is hidden behind a thick veil of interstellar material, making it invisible at X-ray wavelengths. However, the observation of high-ionization emission lines allows its influence to be identified. This discovery highlights JWST’s ability to unravel these mysteries in the early Universe. To make these findings, the researchers used award-winning data from JWST Cycle 2 and combined them with public data from the same telescope. This is also remarkable for Chilean astronomers, because they do not have the benefit of observatories located in the north of the country, which must give 10% of their time to local researchers. A reference is that for the last cycle of use of the JWST there were more than 2,500 applications and only a few will be accepted, which emphasizes the importance of the study carried out by CATA researchers.

More to discover

Some of the signals left by this study is that we can see how these supermassive galaxies formed, which were initially very active, had a lot of gas exchange, formed many stars and then, for certain reasons, stopped doing so and became older or dead elliptical galaxies. “We are witnessing how the early interaction of galaxies is associated with very extensive gas distributions. We already saw that certain gas clouds are being illuminated by an AGN, but there are other clouds that we don’t yet know their origin. A more detailed analysis of the JWST observations will allow us to elucidate where the extended gas is coming from and how it is being excited. Characterizing the current state of the galaxies will allow us to better understand how they will evolve in the future,” adds astronomer Jorge González-López.

What happens to that gas?

“That gas that is inside the system can fall back into the galaxies and generate stars or it can be heated and expelled from the system. What we are seeing now is a snapshot of the gas transport process that occurs during the lifetime of galaxies. The important thing is to learn as much as possible about the current configuration of the gas,” adds the CATA Associate Researcher. Another relevant aspect of the study is that it allowed us to collect much more information that must be processed by the team and that will provide new background information on the evolution of distant galaxies, which will help us to better understand the origins of the Universe.