(ORDO NEWS) — New images of the Spiderweb protocluster galaxy cluster show an unusually high number of active supermassive black holes.
Data from the Chandra X-ray observatory, collected over 8 days, show that in the volume of the explored space, 14 black holes in the hearts of galaxies, including the Web galaxy at the center of the protocluster, are hungry to devour material from the space surrounding them.
This is much higher than in other similar volumes of space, suggesting that up to a quarter of the most massive galaxies in the baby cluster are connected by actively growing black holes.
The Web Protocluster, named after the Web Galaxy at its center, is a growing cluster of galaxies whose light traveled 10.6 billion light-years to reach us.
It refers to a period of cosmic time known as “cosmic noon” – a short period of about 2-3 billion years after the Big Bang, when galaxies formed stars at breakneck speed.
Today, wherever it is, the Web Cluster should have become a massive, stable, gravitationally bound cluster of galaxies.
The study of such clusters, while they are still in the early stages of formation, should provide insight into the evolution of the large-scale structure of the universe. It can also tell us more about the processes that affect the rate of star formation and the activity of supermassive black holes (SMBHs) in galaxy cluster members.
But we don’t know how galaxy clusters evolve, so it’s hard to tell which groups are true protoclusters and which are unlikely to change. For this reason, scientists are looking for unusual, interesting objects that show evolutionary activity confirmed in several wavelength ranges.
Observations of the Web protocluster on Chandra were part of this process. When an SMBH actively accretes material, this process introduces an energy known as “feedback” into the surrounding galaxy, which in turn has a huge impact on star formation.
A team of scientists led by astrophysicist Paolo Tozzi from the National Institute of Astrophysics in Italy pointed a telescope at the cluster to find the characteristic X-ray emission from the supermassive black holes that feed it.
Although black holes themselves do not emit light, the accretion is so energetic that it sends high-energy light into the universe. This is exactly what the team found. In a region of space roughly 11.3 million light-years across, 14 galaxies in the protocluster emitted X-rays, suggesting that their SMBHs are active.
This is much higher than in other similar space samples in the same epoch, with the same range of galaxy masses. Up to 25 percent of the most massive galaxies in the protocluster may have active supermassive black holes, the researchers found. This is five to 20 times more than in other samples.
This could have interesting implications for our understanding of how galaxy clusters grow and how they influence the formation and evolution of galaxies. The find suggests that there is something specific in the environment of the Spiderweb protocluster that provokes the activity of supermassive black holes.
It is not yet clear what this factor might be. Perhaps the gravitational interaction between galaxies is moving material, sweeping it towards galactic centers where it can be consumed by black holes.
Another possibility, the researchers say, is that the protocluster somehow retained a large amount of cold gas, which would be easier for black holes to swallow than the hot gas we see in nearby clusters of galaxies. Or maybe a combination of factors comes into play.
According to the researchers, data from instruments capable of seeing in various wavelengths, including the Hubble Space Telescope, will help shed light on this mystery.
“Using the existing multi-wavelength data set on the Web field, we plan to continue studying the properties of the members of the X-ray protocluster to elucidate the underlying physical mechanism responsible for the production of X-rays,” they write in their paper.
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