Using the Very Large Telescope (VLT) and the Atacama Large Millimeter/Submillimeter Array (ALMA), scientists investigated the brightest cluster of galaxies (BCG) in the MACS 1931.8-2635 cluster. The research results are published on the preprint site.

Clusters of galaxies are made up of thousands of galaxies bound by gravity. These largest gravitationally bound structures are critical to studying large-scale structure formation and the evolution of the universe.

BCGs are usually the brightest clusters in galactic clusters.

At a redshift of approximately 0.35, MACS 1931.8-2635 (M1931 for short) is a massive, X-ray luminous cluster of galaxies with a cool core. Its BCG has a stellar mass of about 590 billion solar masses, and its star formation rate (SFR) is estimated to be high. On average, each year, the cluster adds as much stellar mass as 250 suns weigh.

Previous research has shown that M1931 has one of the coldest X-ray emitting nuclei ever found. BCG also has the largest known cold gas reservoir at the core of the cluster. The mass is equivalent to 19 billion solar masses.

To better understand the nature and evolution of this BCG, a team of astronomers conducted multi-wavelength observations of this galaxy using the Multi Unit Spectroscopic Explorer (MUSE) VLT and ALMA.

The study identified sources of ionization in various regions of the M1931 BCG. It is estimated that about 80% of the cluster’s stellar mass formed over 6 billion years ago. The ICM metallicity of M1931 was found to be consistent with the gas phase metallicity measured in the interstellar medium (ISM) of the BCG. This discovery suggests that the warm gas observed in the galaxy’s ISM was condensed from the ICM.