Current Research Highlights

Observing a supermassive black hole in the distant Universe, MPA astronomers have discovered that it is in the process of stripping gas from a neighbouring galaxy. The gas is being very quickly turned into stars in the black hole’s host galaxy and is allowing the black hole to grow very quickly. This agrees with theoretical predictions that massive galaxies and black holes form with help from mergers with smaller galaxies and bursts of star formation. more

Black holes, resulting from the death of massive stars, are some of the most exotic and powerful objects in the Universe. Since even light cannot escape these objects, the quasi-periodic signals coming from the gas falling into the black hole serve as a probe to infer a great deal of information about the black hole and its surrounding environment. The most-commonly observed quasi-periodic signal is thought to originate from the wobbling of hot gas around the black hole, like a spinning top. One problem, though, is that inferred size of this (isolated) corona seemed to be inconsistent with estimations from other observables. With our recent, state-of-the-art computer simulations, involving a more realistic geometry of the accretion flow, we demonstrated for the first time, that the presence of a disc around the corona significantly slows down its precession, relieving much of the tension between this model and observations. These results thus have important implications for studies of black hole properties and how black hole systems form and evolve. more

The universe today is host to a vast network of galaxies and an even richer array of invisible dark matter structures. But this was not always the case. The universe was nearly uniform until a time of about 100 million years, when the first cosmic structures gravitationally condensed. These objects were made of dark matter alone and each may have weighed no more than the Earth. Most of these objects do not last long: they rapidly grow and cluster together to form the much larger systems that we know today. Despite this, scientists at MPA have discovered in high-resolution simulations that some unique features of the first structures survive this process. Their lingering imprint could manifest itself in astronomical observations, yielding clues to the identity of dark matter. more

Einstein’s General Theory of Relativity predicts that large concentrations of mass – such as galaxies – will bend light rays passing nearby, a phenomenon known as gravitational lensing. When a distant galaxy (the lens) lies exactly between us and an even more distant object (the source), the source is distorted and magnified into several images around the lens galaxy. A group at MPA and other institutes used very long baseline radio interferometry (VLBI) to study a gravitational lens system in high resolution. This reveals extreme detail in the lensed images, and provides a new window into the physics of lens galaxies. more

All stars in galaxies form in the dense gas of the interstellar medium (ISM). Ionizing radiation from newly born massive stars and supernova explosions lets the gas shine at characteristic wavelengths of certain atoms and ions. The relative strength of such line fluxes is an important observational diagnostic to reveal the internal state and composition of the ISM. However, emission by diffuse ionized gas has different flux ratios making accurate predictions difficult. Scientist at MPA and their European collaborators have used supercomputers to simulate a realistic star forming interstellar medium and to quantify the contribution of the diffuse gas. This finding allows for a more accurate interpretation of observations also at early cosmic times when these extreme conditions are more common than in the local Universe.  more

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

Massive stars often reside in multiple star systems, therefore it is expected that mergers of their final stages, neutron stars or black holes, contribute significantly to gravitational wave sources. A team at MPA has now studied the evolution of millions of quadruple star systems and estimated that a significant fraction of the black hole – black hole mergers detected by LIGO come from such multiple star systems rather than simple binaries. more

Different measurements of the Hubble constant, the current expansion rate of our universe, show a discrepancy known as the Hubble tension. This could hint towards new physics beyond the standard model of cosmology. Using a complementary statistical method, researchers at MPA now narrow down possible new physics in the early universe and constrain the fraction of a proposed new component: early dark energy. more

Two types of hot, blue and dense stars that show peculiar characteristics in their composition and vibrations have posed a challenge to astrophysicists for more than a decade. A team of scientists from MPA and La Plata in Argentina, has now been able to explain both types as a product of very similar merger events. In particular, the scientists think that the peculiar hot and blue stars are formed by the merger of two white dwarfs. more

In 2020, a tantalizing hint of new physics violating “parity symmetry” was found in polarization data of the cosmic microwave background obtained with the Planck satellite at high frequencies. Based on the Planck data and a simplified assumption about the impact of the polarized dust emission in the Milky Way, the scientists reported a violation of the symmetry of the laws of physics under inversion of spatial coordinates with 99.2% confidence level. An international team led by MPA director Eiichiro Komatsu has now improved the analysis method. By considering the dust emission explicitly and using more data from not only Planck but also from WMAP the astrophysicists measured the parity-violating signal with 99.987% confidence level. If this should be confirmed in the future as a genuine cosmological signal, it would have profound implications for the fundamental physics behind dark matter, dark energy, and quantum gravity. more

Already in the early Universe, supermassive black holes with masses a billion times larger than the Sun appear to inhabit the centres of massive galaxies. As interstellar gas is accelerated in their powerful gravitational field, it emits copious amounts of radiation, outshining the entire galaxy as “quasars”. Recent observations have revealed that the first quasars are often surrounded by bright, giant nebulae. These can span up to several 100,000 light years, about ten times larger than their host galaxy. New detailed computer simulations of galaxy evolution performed at MPA have shed new light on these puzzling observations, reproducing them in striking detail. According to these new theoretical models, the observed extended nebulae can be explained as quasar light that reflects off cool neutral hydrogen clouds surrounding the quasar host galaxy. Crucially, this mechanism only works if the energy provided by the quasar is able to produce gigantic galactic winds that blow out large masses of gas from its immediate vicinity. This finding suggests that quasars shape galaxy evolution from the earliest stages of galaxy formation. more