A stupid bunch of feeding black holes have been discovered in this cosmic spider web

New images of the Spiderweb protocluster of galaxies reveal an unusually high number of active supermassive galaxies black holes.

Data from the Chandra X-ray Observatory collected over 8 days shows that in the studied space, 14 black holes at the heart of galaxies, including the Spiderweb Galaxy at the center of the protocluster, are hungrily devouring material from space around them.

This is a much higher rate than other similar volumes of space, suggesting that up to a quarter of the most massive galaxies in the baby cluster are bound to actively growing black holes.

The Spiderweb Protocluster, named for the Spiderweb Galaxy at its center, is a growing cluster of galaxies whose light has traveled 10.6 billion light-years to reach us. It dates back to a period in cosmic time known as “Cosmic Noon” – a brief period some 2-3 billion years after Big Bang where galaxies were forming stars at breakneck speed.

Today the Spiderweb Cluster, wherever it is located, should have evolved into a massive, stable, gravitationally bound galaxy cluster.

Studying 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 influence star formation rates and supermassive black hole (SMBH) activity in members of galaxy clusters.

The 14 active SMBHs with the Spiderweb Galaxy in the center. (NASA/CXC/INAF/P. Tozzi et al./NAOJ/NINS/STScI)

But we don’t really know how galaxy clusters evolve, so it’s difficult to determine which groups are true protoclusters and which are unlikely to change. For this reason, scientists are looking for unusual targets of interest that have evolutionary-related activity that has been confirmed across multiple wavelengths.

The Chandra observations of the Spiderweb protocluster were part of this process. When an SMBH is actively enriching material, the process injects energy known as “feedback” into the surrounding galaxy, which in turn has a massive impact on star formation.

A team of scientists led by astrophysicist Paolo Tozzi from the National Institute for Astrophysics in Italy trained the telescope on the cluster to look for the telltale X-ray emission from feeding supermassive black holes.

Although the black holes themselves don’t emit light, the accretion is so energetic that it sends high-energy light through the universe. The team found that out. In a region of space about 11.3 million light-years across, 14 of the galaxies in the protocluster have been observed to emit X-rays, suggesting their SMBHs are active.

Spider Web GalaxyA multi-wavelength image of the Spider’s Web Galaxy. (NASA/CXC/INAF/P. Tozzi et al./NAOJ/NINS/STScI)

This is much higher than other similar space examples of the same epoch with the same range of galaxy masses. Up to 25 percent of the most massive galaxies in the protocluster could have active supermassive black holes, the researchers found. This is five to twenty times higher than other samples.

This could have interesting implications for our understanding of how galaxy clusters grow and influence galaxy formation and evolution. The finding suggests that there is something specific in the spiderweb protocluster environment that triggers supermassive black hole activity.

It is unclear what this environmental factor might be. It is possible that the gravitational interactions between the galaxies are moving material and sweeping it towards the galactic centers where it can be gobbled up by the black holes.

Another possibility, the researchers said, is that the protocluster somehow retained a large amount of cold gas that would be easier for the black holes to accrete than the hot gas we see in nearby galaxy clusters. Or maybe a combination of factors are at play.

Data from instruments that can see into different wavelengths, including the Hubble Space Telescope, should help shed some light (ha ha) on this mystery, the researchers said.

“By utilizing the available multi-wavelength dataset on the Spiderweb field, we plan to further probe the properties of the X-ray protocluster members to investigate the key physical mechanism responsible for triggering X-ray emission,” they wrote in their newspaper.

The research was accepted Astronomy & Astrophysicsand is available at arXiv.

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