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Galaxy clusters are our universe's largest gravitationally bound systems, extending out to several million light-years and hosting up to 1000 galaxies. The matter permeating the clusters is known as the “intracluster medium” (ICM), a very hot and ionized gas (T~ 10-100 million K) emitting bright X-rays due to thermal bremsstrahlung. Scientists from MPA and the University of Heidelberg have discovered that the ICM also contains a significant amount of cool gas (10,000 K) up to large distances. The statistical connection between the haloes of cluster galaxies and absorption features points toward a complex origin of this cool gas where clouds are either associated with satellite galaxies or were previously stripped from their haloes. more

Galaxies are embedded in large reservoirs of gas - mostly hydrogen and helium. This hydrogen gas has been found to glow faintly in a specific ultraviolet wavelength, or color, called Lyman-alpha. Scientists at the MPA have discovered that these Lyman-alpha halos are larger than previously thought, spanning several 100,000 light years. The inferred size and shape of the halos suggest that the light in the outer parts of the halos comes from surrounding galaxies or the gas in their environments rather than from the central galaxy itself. more

A new study of galaxies with data from the MaNGA survey shows that the initial mass function of stars, i.e. the mass distribution when they initially form, might not be as universal as widely assumed. The MPA study found an excess of very massive stars in some galaxies. An excess of radio sources in the sample might be an intriguing hint that a hidden population of black holes may exist in these galaxies. more

In the interstellar medium (ISM) of galaxies, stars form in small groups groups of a few hundred and clusters up to several million stars. A full theoretical model of this process and its impact on galaxy evolution is still in its infancy. MPA researches and their collaborators have developed a highly complex numerical model to simulate the multi-phase ISM and how star clusters emerge in dwarf galaxies. The supercomputer simulations show that the properties of the star clusters depend on how efficiently stars can form from the cold dense gas. Detailed post-processing then allowed the researchers to compare their results to observations. This demonstrates the scientific fidelity of the new model, its current limitations, and observational limitations on how well clusters can be detected in regions of high star formation activity. The studies are a major step towards a comprehensive model for star cluster formation. more

The colours and star formation rates of galaxies are strongly correlated with each other out to distances as large as 10 Megaparsecs. However, current galaxy formation models fail to reproduce these large-scale correlations accurately. Scientists from MPA, the University of Surrey, and Heidelberg University are in the process of updating the Munich galaxy formation model, L-GALAXIES, with a sophisticated and accurate method to model environmental effects for all galaxies. The most recent updated model is in significantly better agreement with observations than its predecessors and exhibits a stronger environmental dependency of galaxy properties out to several Megaparsecs from the centers of their dark matter haloes. more