Astronomers note the light within the cluster – the elusive glow between distant galaxies

Astronomers note the light within the cluster -- the elusive glow between distant galaxies

The light “between” galaxy clusters – the “light within the cluster” – however faint, radiates from stars stripped of their home galaxy. Photo: attached. Source: Martínez-Lombilla et al./UNSW Sydney

An international team of astronomers has turned new technology to a cluster of galaxies and the faint light between them – known as “inner group light” – to discern the stars that dwell there.

The lead author of the study published in MNRASDr Cristina Martinez Lumbela, from UNSW’s School of Physics, said: “We know almost nothing about the light within the group.

“The brightest parts of the light within the cluster are about 50 times dimmer than the darkest night sky on Earth. They are extremely difficult to detect, even with the largest telescopes on Earth — or in space.”

Using their sensitive technology, which eliminates light from all objects except the light from within the cluster, the researchers not only detected light within the cluster, but were able to study and tell the story of the stars that inhabit it.

“We analyzed the properties of the stars within the cluster – those stray stars between galaxy clusters. We looked at the age and abundance of the elements that make it up and then compared those features to the stars they still belong to galaxy clusterssaid Dr. Martinez Lumbela.

“We found that the inner light of the cluster is younger and less mineral-rich than the periphery galaxies. ”

Reconstruct the story of light within the group

Not only were the orphan stars in view of the inner group “obsolete,” they seemed to be of a different origin than their closest neighbors. The researchers found that the personality of the stars within the cluster looks similar to the mysterious “tail” of a distant galaxy.

Combining these clues allowed the researchers to reconstruct the history — the story — of light within the cluster and how its stars were assembled in their stellar orphanage.

“We believe that at some points these individual stars have been stripped of their original galaxies, and are now floating freely, according to the gravity of the group,” said Dr. Martinez Lumbela. “The stripping, called tidal stripping, is caused by the passing of massive satellite galaxies — similar to the Milky Way — dragging stars in their wake.”

This is the first time that light has been observed within the cluster for these galaxies.

“Revealing the quantity and origin of the inner group light provides a Fossil record among all the interactions experienced by a group of galaxies and provides a comprehensive view of the system’s interaction history,” said Dr Martinez Lumbela.

Also, these events happened a long time ago .. galaxies [we’re looking at] So far away that we notice them as they were 2.5 billion years ago. That’s how long it takes for their light to reach us.”

By observing events from long ago, in distant galaxies, researchers are contributing vital data points to the slow evolution of cosmic events.

Custom image processing procedures

The researchers devised a unique method to achieve this insight.

“We have developed a custom image-processing procedure that allows us to analyze the weakest structures in the universe,” said Dr. Martinez Lumbela.

Follows the standard steps for studying faint structures in astronomical images—which includes 2D modeling and removing all but the light coming from the light within the cluster. This includes all bright light. stars In the images, the galaxies block the light within the cluster and subtract the continued emission from the sky.

“What makes our method different is that it is entirely Python-based, so it is very modular and easily applicable to different sets of data from different telescopes rather than being useful only for these images.

“The most important finding is that when studying very faint structures around galaxies, every step in the process matters and every unwanted light must be accounted for and removed. Otherwise, your measurements will be wrong.”

Dr. Martínez-Lombilla said the techniques presented in this study are experimental, and encourage future analyzes of light within the group.

“Our main long-term goal is to extend these results to a large sample of the galaxy cluster. Then we can look at the statistics and see typical characteristics related to the formation and evolution of the intercluster. light These are very common systems of galaxy clusters.

“This is key work to prepare the next generation of deep, whole-sky surveys such as those to be conducted with the Euclid Space Telescope and the LSST with the Vera C. Rubin Observatory.”

more information:
Cristina Martínez-Lombilla et al, Galaxy And Mass Assembly (GAMA): intra-cluster stretched light in an array at z = 0.2 Hyper Suprime-Cam depth images, Monthly Notices of the Royal Astronomical Society (2022). DOI: 10.1093/mnras/stac3119

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