Quantum fluctuations in the very early Universe give rise to anisotropies in the cosmic microwave background, and seed present-day cosmic structures. In addition, these fluctuations generate primordial gravitational waves, which are weakly non-Gaussian. However, primordial gravitational waves can also be generated by other sources. Scientists at MPA recently showed that the level of non-Gaussianity, the skewness, can be used as an important test of the origin of primordial gravitational waves.
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.
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. 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.
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.
Astrophysicists from Heidelberg, Garching, and the USA gained new insights into the formation and evolution of galaxies. They calculated how black holes influence the distribution of dark matter, how heavy elements are produced and distributed throughout the cosmos, and where magnetic fields originate. This was possible by developing and programming a new simulation model for the universe, which created the most extensive simulations of this kind to date.
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.
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.
In observations of galaxy clusters, astronomers in collaboration with the MPA discovered a new class of cosmic radio sources. With the digital radio telescope Low Frequency Array (LOFAR) they received the longest radio waves that can be measured on Earth. They identified a remarkable "tail"behind a galaxy in the radio light, which must have been re-energized after it had faded away.
Last week the Gruber foundation announced that this year’s cosmology prize is awarded to the Planck team, which includes scientists at the Max Planck Institute for Astrophysics (MPA). From 2009 to 2013 the European Space Agency’s Planck observatory collected data that has provided cosmology with the definitive description of the universe on the largest and smallest scales. “These measurements,” the Gruber Prize citation reads, “have led to the determination of cosmological parameters (matter content, geometry, and evolution of the universe) to unprecedented precision.”
Gravitational lensing is becoming increasingly important for the study of distant galaxies and dark matter. Two groups have recently detected transient events emanating from far-away lensed galaxies, apparently due to extreme magnification of individual stars. MPA researchers Giulia Chirivì and Sherry Suyu contributed to the mass modelling of the galaxy cluster MACS J0416.1-2403, one of the most efficient lenses in the sky. In 2014, the Hubble Space Telescope observed two unusual transient events that appeared behind the galaxy cluster in a strongly lensed galaxy at z~1, faster and fainter than any supernova, but significantly more luminous than a classical nova. The findings are published in Nature Astronomy by Rodney et al. (2018).