China News Service, Nanjing, March 5 (Xu Shanshan) According to news from the Purple Mountain Observatory of the Chinese Academy of Sciences on the 5th, an international team led by researchers from the observatory discovered a pair of massive, quiet galaxies that may be merging in the dense region at the core of the protogalaxy cluster, revealing that The brightest cluster galaxies are formed before the proto-galaxy cluster relaxes.
This provides important observational constraints for understanding the formation of the brightest cluster galaxies at high redshifts and the termination mechanism of star formation in massive galaxies.
Galaxy clusters are the densest systems in the large-scale structure of the universe. In their centers are a type of supermassive elliptical galaxies called the brightest cluster galaxies.
Due to their extreme formation conditions, such galaxies are often used to test theoretical models of the formation of massive galaxies, galaxy clusters and large-scale structures.
However, its formation mechanism remains a mystery.
"Currently, people's observational research on the brightest cluster galaxies is limited to virialized galaxy clusters. It is not clear whether the growth of such galaxies is crucial for the formation of mature galaxy clusters. Therefore, direct observation of protogalaxy clusters in the early universe It is of great significance to understand the relationship between the brightest cluster galaxies and their host galaxy clusters, as well as their formation and evolution." said Shi Dongdong, a postdoctoral fellow at the Purple Mountain Observatory of the Chinese Academy of Sciences.
Researchers used the near-infrared seamless spectrum and a series of observation data from the International Space Telescope Hubble to discover a pair of massive and quiet galaxies that may be merging. They have an elliptical shape, obvious Balmer and other absorption features, and live in proto-galaxy clusters. The densest region of the core.
Based on cosmological model estimates, the researchers found that even if the two galaxies eventually merged to form a more massive mature brightest cluster galaxy, it still occurred before the proto-galaxy cluster became energized.
Interestingly, the research team also discovered for the first time that the star formation activity of protocluster galaxies presents a significant gradient distribution from its dense core to the periphery, that is, the densest core region is a quiet galaxy, and the medium density region is a normal star-forming galaxy. , the low-density outer region is a submillimeter-wave galaxy with intense star formation activity.
Relevant research results were published in the international astrophysical journal "The Astrophysical Journal".
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