Scientists are studying the SPT2349-56 galaxy cluster that we see as it was when the Universe was young. They found a huge cloud of hydrogen in it. Apparently, it’s fueling the star formation that’s going on there.
Cluster of galaxies
Astronomers using the Atacama Large Millimeter / Submillimeter Array (ALMA), as well as additional data from the Atacama Pathfinder Experiment (APEX), have discovered a surprisingly large supply of molecular gas in a protoscope of galaxies known as SPT2349-56. This proto-cluster, located about 12 billion light-years away, is a region of the early Universe where a cluster of galaxies is just beginning to form.
Galaxy clusters are the largest structures in the Universe, and understanding their formation is a major goal of scientists. Proto-clusters such as SPT2349-56 offer a unique window into this process, allowing astronomers to observe galaxies as they come together in a dense environment.
This new study led by Dazhi Zhou of the University of British Columbia, published in The Astrophysical Journal Letters, focuses on the molecular gas in SPT2349-56. Molecular gas, primarily hydrogen, is the raw material for star formation, which plays a crucial role in the evolution of galaxies.
Key findings of the study
Missing gas: By comparing observations from the high-resolution ALMA configuration with lower-resolution data from the Atacama Compact Array (ACA) and APEX, the team found a significant amount of molecular gas that was “invisible” in the high-resolution ALMA images. ACA detected 75% more CO than the sum of the individual sources detected in the high-resolution ALMA data.
Extended reservoir: The missing gas is not just a few faint, undetected galaxies. Instead, it appears to be a diffuse reservoir of gas spread throughout the protoscope.
Fuel for starbursts: This hidden reservoir of gas may be the key to understanding the intense star formation activity observed in SPT2349-56. The presence of so much extra gas increases the fuel supply for star formation, meaning that the total depletion time will exceed 400 million years.
Proto-intracluster medium: The team suggests that this expanded gas may be a precursor to the hot diffuse gas known as the intracluster medium that fills mature galaxy clusters.
“This discovery emphasizes the power of ALMA, especially when used in multiple configurations,” Zhou said. “The high-resolution observations allowed us to pinpoint individual galaxies, while the lower-resolution data revealed the bigger picture – the extended gas that connects these galaxies and fuels their star formation.”
Extreme star formation in a galaxy cluster
SPT2349-56 is an extreme system that forms stars about 10,000 times faster than our Milky Way but is comparable in size, and these observations have pushed scientists toward understanding the formation and evolution of galaxies. No simulation or model of galaxy formation has previously suggested such excessive gas density.
These results also suggest that high-resolution ALMA observations, although excellent for studying individual galaxies, may miss a significant component of gas in these early clusters. The missing gas may be in the circum-galactic medium (CGM) or in the pre-heated proto-intracluster medium (proto-ICM).
Future studies using the full capabilities of ALMA, including compact lattice configurations, will be crucial to fully characterize this hidden gas reservoir and understand its role in the formation of galaxy clusters.
According to phys.org
