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Approximately 13 billion years ago, the radiation produced by the first galaxies completely transformed the Universe. The vast amount of hydrogen filling the space between galaxies was  ionized in a process called cosmic reionization. Despite their intimate connection, the formation of the first galaxies and the reionization process are typically studied separately. An international team led by and including MPA researchers has now produced the first suite of simulations designed to simultaneously investigate these two processes during the infancy of the Universe, unveiling features of their connection. This new numerical effort – soon to be released publicly – provides a unique platform for investigating the young Universe and to fully exploit the forthcoming James Webb Space Telescope. The first results from THESAN have already shown that its unique combination of physical accuracy and simulated scales allows to reproduce most of the available data, including some that escaped previous numerical efforts. more

Cosmological simulations show that the growth of galaxies in the early Universe is regulated by the interplay between gas accretion onto dark-matter halos and ejection of matter by stars and active galactic nuclei (AGN). While these processes are routinely described in theoretical works, still little is known from observations on the complex exchanges of mass and energy within the halos of galaxies, where large-scale infall (i.e. accretion) meets outflows (i.e. ejection). Recently, an international team of astronomers was able to probe the halo gas of a massive galaxy system, SMM J02399-0136, using a novel approach. These observations unveiled – for the first time – the infall towards the galaxies of a large mass of diffuse, highly turbulent multiphase gas, pervaded by powerful outflows and more than 10 times larger than the star-forming galaxies. more

Magnetic fields are ubiquitous in the Universe today, from stars to clusters of galaxies. Their origin, however, remains a mystery. MPA researchers have now simulated in great detail a variety of proposed mechanisms for magnetogenesis – i.e. how magnetic fields might be created – in high-redshift galaxies. They also studied their impact on the formation and evolution of galaxies, providing guidance to both future observations and simulations. Their work demonstrates that high-redshift galaxies may hold the key to understanding the origin of cosmic magnetic fields. It also provides the first-ever investigation on galactic scales of a novel magnetogenesis mechanism. more

Intermediate mass black holes (IMBH) should be linking observed stellar black holes and supermassive black holes, but their formation mechanisms are still debated. Young and dense massive star clusters are promising environments for the formation of such black holes through collisions. An international team lead by MPA researchers has presented novel realistic simulations of star clusters, where these missing links form by rapid collisions of stars and black holes. The study also predicts an IMBH formation channel by the merging of black holes in a mass regime, which is excluded by stellar evolution models. In this “mass gap” a black hole merger has indeed been observed recently by the LIGO/Virgo gravitational wave collaboration. more

Where are the baryons? This question naturally arises as the predicted abundance of baryons in the universe - the basic building blocks of all elements in the periodic table – do not agree with observations of the intergalactic medium. Locating the missing baryons will help us to not only better understand the formation and evolution of galaxies, but also to better constrain possible extensions of the current standard model of cosmology. MPA researchers have turned to a novel approach in modelling the galaxy distribution to optimize measurements of the kinematic Sunyaev-Zel'dovich effect, an emerging tool to probe the distribution of baryons in galaxy clusters. more

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