Highlights 2020

Dark matter is the most abundant matter component in the universe. But while it influences all structure in the universe, its nature is still unknown. Among the many candidates is ultra-light dark matter, the lightest possible candidate for dark matter, which been receiving a lot of attention recently, as this might be probed by current and future experiments. MPA researchers have written a review on the current status of these models and their search for observational markers, introducing a division into three classes and showing how the rich phenomenology of this leading candidate for dark matter could help answer the question of what dark matter really is. more

Recently, astronomers discovered an extended glow of emission far beyond the stellar bodies of galaxies. While the emission is known to be associated with excited neutral hydrogen, the origin of this so called Lyman-alpha radiation is unknown. MPA researchers use new computational models to understand this emission, establishing that a large contribution is caused by light which originates from deep within galaxies but subsequently scatters at much larger distances. more

The Planck satellite mission to measure the cosmic microwave background radiation – the echo of the Big Bang – was completed in September 2020 with the publication of the final set of publications. In addition to groundbreaking insights into cosmology, the ESA mission also provided a large number of astrophysical results. A brief review. more

The origin of mysterious fast radio bursts (FRBs) has been debated since their discovery in 2007. A theory developed at Columbia University and MPA suggested that FRBs are emitted by blast waves from flaring magnetars -- neutron stars with ultrastrong magnetic fields. On 28 April 2020, an FRB was detected from SGR 1935+2154, a known magnetar in our Galaxy. A new numerical experiment demonstrates how perturbations can grow in a magnetar and launch a magnetic explosion – and a burst such as the observed one. more

When interstellar gas falls towards a supermassive black hole, it liberates vast amounts of energy - so vast as to be capable of ejecting much of a galaxy’s gaseous reservoir. Ultimately, supermassive black holes may thus deprive themselves of further fuel and bring about the end of their own growth and that of their host galaxies. A new model developed at MPA now makes it possible to simulate winds accelerated by accreting black holes in galaxy evolution simulations in a physically accurate and validated way. By blowing dense gas from the galactic nucleus, and by halting inward flows from the galactic halo, the winds play a vital role in shaping the evolution of the black hole host galaxy. more

Recently, in correspondence with the 10^th birthday of LOFAR, a core group of researchers including MPA scientists published the most stringent upper limits on the reionization signal from the early Universe. These observations are able to exclude some reionization models and constrain the thermal and ionization state of the intergalactic medium when the Universe was still in its infancy. more

Extracting cosmological information from galaxy surveys is a difficult task – one to which MPA researchers are now one step closer. Using a theoretical framework known as effective field theory combined with a novel statistical approach, they were able to correctly recover the input cosmology based on a catalog of simplified simulated galaxies. more

About 10 billion years ago, a galaxy smashed into our cosmic home, the Milky Way, in a violent “merger” event that changed the way the Galaxy looks. Researchers from MPA together with international collaborators from the UK, Chile and Italy, have managed to piece together the impact of this event using the largest and most sophisticated simulations of the Milky Way to date. In particular, they found that the damage inflicted on the Galaxy in its youth is commensurate with a satellite that weights about a billion Suns. more

Warm, cold, just right? The analysis of seven strongly gravitationally lensed quasars gives new clues about the temperature of dark matter, the mysterious substance that makes up about a quarter of our universe. The results put a lower limit on the mass of a potential dark matter particle while not ruling out cold dark matter. more

A new model of galaxy formation will help scientists to better understand the distribution of gas and stars within galaxies. Researchers from the MPA in Garching, along with collborators from Switzerland, China, the UK, and Iceland have come together to release L-GALAXIES 2020, the latest version of the L-GALAXIES model project, a computational simulation designed to study many millions of galaxies simultaneously, each self-consistently evolved over billions of years of cosmic time. more

Artificial intelligence expands into all areas of the daily life, including research. Neural networks learn to solve complex tasks by training them on the basis of enormous amounts of examples. Researchers at the Max Planck Institute for Astrophysics in Garching have now succeeded in combining several networks, each one  specializing in a different task, to jointly solve tasks using Bayesian logic in areas none was originally trained on. This enables the recycling of expensively trained networks and is an important step towards universally deductive artificial intelligence. more

By examining the Auriga suite, a large sample of simulated Milky Way galaxies formed in the full cosmological context, scientists at MPA have been able to place constraints on the history of the Milky Way's formation. By comparing these simulations to observations of the Milky Way — and specifically to how fast stars of different metallicities in the inner regions of the Galaxy move around its centre — they were able to exclude certain formation histories. In particular they found that our galaxy had to be quite isolated with the last major merger happening over 12 billion years ago and with a galaxy less than 10% of the mass of the Milky Way. more