Feasting Black Holes Caught in Galactic Spiderweb

Often, a spiderweb conjures the idea of captured prey soon to be consumed by a waiting predator. In the case of the “Spiderweb” protocluster, however, objects that lie within a giant cosmic web are feasting and growing, according to data from NASA’s Chandra X-ray Observatory.

The Spiderweb galaxy, officially known as J1140-2629, gets its nickname from its web-like appearance in some optical light images. Located about 10.6 billion light years from Earth, the Spiderweb galaxy is at the center of a protocluster, a growing collection of galaxies and gas that will eventually evolve into a galaxy cluster.

To look for growing black holes in the Spiderweb protocluster, a team of researchers observed it for over 8 days with Chandra. Most of the “blobs” in the optical image are galaxies in the protocluster, including 14 that have been detected in the new, deep Chandra image. These X-ray sources reveal the presence of material falling towards supermassive black holes containing hundreds of millions of times more mass than the Sun. The Spiderweb protocluster exists at an epoch in the Universe that astronomers refer to as “cosmic noon”. Scientists have found that during this time — about 3 billion years after the Big Bang — black holes and galaxies were undergoing extreme growth.

The Spiderweb appears to be exceeding the lofty standards of even this active period in the Universe. The 14 sources detected by Chandra imply that about 25% of the most massive galaxies contain actively growing black holes. This is between five and twenty times higher than the fraction found for other galaxies of a similar age and with about the same range of masses.

Astronomers are investigating what could be causing this high rate of growth around the Spiderweb. It could have to do with collisions of galaxies that happened earlier or it might be due to more cold gas than is expected, which could act as fuel for black hole growth. Future observations with Chandra and other telescopes may provide more answers to the questions surrounding the Spiderweb and its host protocluster.

Credit: NASA/CXC/A. Hobart

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