BEAMS (Brightest cluster galaxy Evolution with ACT, MeerKAT and SALT) is a Large Science Programme on the Southern African Large Telescope (SALT).

Brightest cluster galaxies (BCGs) are the most massive galaxies in the universe, and are found in special environments: the centres of galaxy clusters, which are in turn the most massive gravitationally bound structures in the universe. In fact, clusters are so massive that they have “atmospheres” of hot (10-100 million Kelvin) gas, which is detectable at X-ray and millimetre wavelengths.

The BEAMS project aims to observe around 150 BCGs in galaxy clusters detected by the Atacama Cosmology Telescope (ACT) using the Sunyaev-Zel’dovich (SZ) effect. We target clusters over the redshift range 0.3 < z < 0.7, which covers a 3.4 Gyr time period. We will measure the growth of BCGs over time through cannibalism of their neighbours, and the evolution of their stellar populations. We will also study the evolution of their star formation activity, and the impact of the supermassive black holes that they host on the surrounding cluster environment. To do this, we will combine the ACT and SALT data with MeerKAT observations at radio wavelengths.