Highlights 2018

Astrophysicists at MPA along with an international team of scientists have made a measurement of all the light in the universe, the so-called Extragalactic Background Light (EBL). The EBL is a sea of photons (particles of light) that have been gradually accumulating since the first stars started shining, shortly after the Big Bang. The results are published in Science on November 30th. more

Strong gravitational lensing is an extremely powerful tool to go beyond the current limits in angular resolution and to investigate the high-redshift, i.e. distant Universe. Scientists at MPA take advantage of this phenomenon to perform a detailed study of 17 Lyman-α-galaxies and present an analysis of the sizes and star formation rates of their reconstructed ultra-violet (UV) continuum emission. more

Some stars are observed to rotate with extremely long periods, the ‘slow rotation problem’. A theory developed at MPA now shows how the magnetic field of a star’s ‘birth cloud’ can cause some stars to accumulate mass without acquiring significant rotation. more

Supermassive black holes (SMBH) of up to tens of billon solar masses are hiding in the centers of giant elliptical galaxies. At the same time, these galaxies have ‘missing’ nuclear light as the stellar densities at their cores are much lower than in other giant galaxies. A team of researchers at the University of Helsinki and the astronomical Max Planck Institutes in Garching have used a newly developed simulation technique to investigate the origin of this ‘missing’ light with realistic galaxy models. When two massive elliptical galaxies merge, many central stars are expelled during the final coalescence of the stellar nuclei and their SMBHs. This new model can explain the simultaneous formation of the most diffuse giant galaxy cores as well as other observed core properties such as decoupled rotation and anisotropic stellar velocity distributions. more

Gravitational lensing offers the possibility to study faint, far-away galaxies. MPA researchers have now developed the first three dimensional lens modelling method, which allows not only the reconstruction of the mass distribution of the foreground galaxy but also the kinematics of the background galaxy. Consequently, the matter content can now be studied also in young galaxies.  more

Oxygen, after hydrogen and helium, is the most abundant element in the universe. It is a fundamental tracer to learn more about the formation of single stars as well as entire galaxies. Understanding the origin of highly excited states of oxygen in the circumgalactic medium (CGM) around galaxies has proven difficult, and past theoretical models have had difficulty matching observational constraints. Using cosmological simulations from the IllustrisTNG suite, researchers at MPA have demonstrated how the feedback from supernovae and supermassive black holes can shape the heavy element content of the CGM, bringing it into agreement with data from the local universe. The amount of highly ionized oxygen around blue, star-forming galaxies is predicted to be noticeably higher than around red, quenched systems of exactly the same mass. more

Quantum fluctuations in the very early Universe give rise to temperature and polarisation anisotropies in the cosmic microwave background, and seed present-day cosmic structures. Primordial gravitational waves generated by these fluctuations carry information about the energy scale of inflation, and they are weakly non-Gaussian. However, primordial gravitational waves can also be generated by other sources, and carry imprints of the energy content of the early Universe. Scientists at MPA recently showed that these gravitational waves can be highly non-Gaussian, with a skewness much larger than for those generated by vacuum fluctuations. They concluded that non-Gaussianity is thus an important test of the origin of primordial gravitational waves. more

Previous studies of large AGN samples both a low and at high redshifts seemed to rule out galaxy mergers as the drivers for black hole growth. A new technique developed at MPA for selecting a rare type of active galactic nuclei now show that it is possible to identify a new class of AGN in which more than  80% of the galaxies turn out to be merging or interacting systems, with clear indications of an accreting black hole. A detailed statistical analysis then reveals that mergers drive  black hole formation in the most massive galaxies in the local Universe. more

At the very beginning of the Universe, not only elementary particles and radiation were generated but also magnetic fields. A team of researchers led by the Max Planck Institute for Astrophysics now calculated what these magnetic fields should look like today in the local universe – in great detail and in 3D. To achieve this, first they traced back the current distribution of matter to the time of the Big Bang; this distribution of matter was then used to calculate the generation of the magnetic field; and finally the resulting fields were translated back to the present. Thus, the researchers were able to predict the structure and morphology of the primordial magnetic field in our cosmic neighbourhood for the first time. This field is incredibly weak; nevertheless, the prediction could help to address the challenge of measuring it. more

Buoyant bubbles of relativistic plasma in galaxy cluster cores plausibly play a key role in conveying the energy from a supermassive black hole to the intracluster medium (ICM). While the amount of energy supplied by the bubbles to the ICM is set by energy conservation, the physical mechanisms involved in coupling the bubbles and the ICM are still being debated. A team of researchers from the Max Planck Institute for Astrophysics (MPA) and the University of Oxford argues that internal waves might be efficient in extracting energy from the bubbles and distributing it over large masses of the ICM. more

Modified gravity models often contain some form of screening to reduce to general relativity in our immediate cosmic neighbourhood. Scalar waves from astrophysical or cosmological events were thought to significantly disrupt this screening of the Solar System, invalidating previously viable modified gravity models. MPA scientists show that disruptions are actually generally negligible for physically relevant setups. more

Neutron stars are the densest objects in the Universe; however, their exact characteristics remain unknown. Using recent observations and simulations, an international team of scientists including researchers at the Max Planck Institute for Astrophysics (MPA) has managed to narrow down the size of these stars. Thus the scientists were able to exclude a number of theoretical descriptions for the neutron star matter. more