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JWST observations shed more light on the nature of a distant galaxy cluster

JWST observations shed more light on the nature of a distant galaxy cluster

The RGB composite color image of the CL J1001. Credit: Sun et al, 2024

Astronomers from Nanjing University in China and elsewhere have made high-resolution observations of a distant galaxy cluster known as CL J1001+0220 using the James Webb Space Telescope (JWST). The observation campaign, described in an article published March 8 on the preprint server arXivprovides important information about the nature of this cluster.

Galaxy clusters contain up to thousands of galaxies held together by gravity. They are the largest known gravitationally bound structures in the universe and could serve as excellent laboratories to study evolution of the galaxy and cosmology.

CL J1001+0220 (or CL J1001 for short) is a galaxy cluster in the Sextans constellation, containing 17 galaxies, located at a distance of approximately 11.1 billion light years. It exhibits an enhanced star formation rate (SFR), short gas depletion time, and presents strong evidence that the properties of its member galaxies are affected by the extreme environment.

Previous studies have shown that J1001 appears to undergo transformation from a protocluster to a mature cluster. Since such evolution is not fully understood, a team of astronomers led by Hanwen Sun of Nanjing University decided to examine this process more closely using the Near Infrared Camera (NIRCam ) of the JWST. Their study was supplemented by data from ground telescopes such as the Subaru Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA).

“Here we present new JWST/NIRCam observations targeting the distant cluster CL J1001 at z = 2.51 from the COSMOS-Webb program, which in combination with previous narrowband imaging targeting Hα emitters and deep millimeter studies CO emitters, provide a comprehensive view of the massive galaxy assembly in CL J1001,” the researchers wrote in the paper.

Sun's team succeeded in carrying out a census of the member galaxies of CL J1001. First, they identified a population of red, massive cluster members, which had been missed in previous deep imaging using the Hubble Space Telescope (HST). This confirms that JWST observations are necessary to obtain a complete census of members of galaxy cluster.

The study revealed that the spatial distribution of member galaxies of CL J1001 is very concentrated. Astronomers noted that the central stellar density of CL J1001 is comparable, or even greater, than that of more massive clusters at low redshift, unlike what is observed at the periphery of this cluster. These results suggest a reverse formation scenario for the first known clusters.

Additionally, based on the full mass sample of star-forming members, astronomers found that CL J1001's stellar mass function exhibits a prominent “top-heavy” feature because there is an overabundance of massive galaxies. star forming (SFG). crammed into the cluster core. It was found that the total number and stellar density of these massive SFG members are comparable to those of massive SFG galaxies and quiescent galaxies combined in clusters at lower redshifts.

Summarizing the results, the paper's authors concluded that CL J1001 is currently in a rapid transition and that many of its massive SFGs will likely soon become inactive.

More information:
Hanwen Sun et al, JWST's first glimpses of the forming cluster az > 2 reveal a very heavy stellar mass function, arXiv (2024). DOI: 10.48550/arxiv.2403.05248

Journal information:

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