Researchers, led by the Kavli Institute, have identified the COSTCO-I galaxy protocluster as a significant discovery, revealing early heating of portions of the universe to temperatures consistent with today’s Warm-Hot Intergalactic Medium (WHIM). This protocluster, discovered in 2022, has a mass exceeding 400 trillion times that of the Sun and spans several million light-years. Interestingly, the researchers observed a surprising absence of hydrogen absorption in the area, which is typically present due to neutral hydrogen associated with protocluster gas. This suggests that the gas within COSTCO-I is heated to temperatures potentially exceeding one million degrees—much hotter than expected for the universe at that epoch, when it was merely 3 billion years old.
The findings may provide insight into the evolution of galaxy protoclusters and the dynamics of the intergalactic medium, which contains the majority of the universe’s atoms. Understanding the mechanisms behind this heating, potentially from gravitational collapse or energy from supermassive black holes, could shed light on gas behavior influencing galaxy formation. The upcoming Subaru Prime Focus Spectrograph will allow astronomers to explore these phenomena further, expanding the search for similar protoclusters and enhancing our understanding of the early universe’s evolution.
