Highlights 2022

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

Are galaxy orientations distributed randomly in the cosmos? What appears to be a simple question might not only shed light on our understanding of galaxy and cluster formation, but also further our knowledge of cosmological models. MPA scientists and collaborators attempt to settle this question through the first direct, field-based measurement of whether and how massive red elliptical galaxies align with the tidal field of large scale structure. Their result confirms predictions of the (linear) alignment model of galaxy intrinsic alignment. The newly presented method also opens up new avenues for cosmology and astrophysics. more

Magnetic fields of spiral galaxies usually show spiral structures themselves. For our own galaxy, this could not be confirmed so far due to our unfavorable inner perspective. Researchers at the Max Planck Institute for Astrophysics have now shown that the local galactic magnetic field is indeed aligned with the local Orion spiral arm of the Milky Way, as expected for a spiral galaxy. 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 April 2017 the Event Horizon Telescope (EHT) observed the super-massive black hole M87* and provided a first image of its shadow that went around the world. Researchers at the Max Planck Institute for Astrophysics have now reconstructed a video of the immediate surroundings of a black hole from the same underlying data. This not only confirms previous findings, it also hints at new structures and dynamics in the gas disk around the black hole. more