Cosmology News

Rather than trying to study special regions in large-volume simulations, scientists at MPA have used the IllustrisTNG model to create whole separate universes with a modified cosmology. Their study of these separate universes shows that when the baryon density (the density of ordinary matter) changes, the number of galaxies can increase or decrease depending on how this number is measured. Also, the large-scale distribution of matter is affected by the effects of baryons, with various measures reacting differently. more

Quasars are amongst the brightest non-transient sources in the sky. Thanks to their high luminosity, they can be observed even at early cosmic times, where – surprisingly – these first quasars appear as already evolved systems: with black holes with masses exceeding one billion solar masses hosted by massive and heavily star forming galaxies. To explain such rapid growth, theorists believe these systems must reside in peculiarly dense environments, where huge gas reservoirs favour efficient inflow of material onto seed super-massive black holes. An international team of astronomers has recently found the first clear observational evidence that this is indeed the case. The new “panoramic” spectrograph called MUSE unveiled, for the first time, the almost ubiquitous presence of large amounts of cool gas in close proximity to the first quasars. This pristine fuel will fall on the primordial galaxies and sustain their growth in both stellar and black hole mass. more

The expansion rate of the Universe today is described by the so-called Hubble constant and different techniques have come to inconsistent results about how fast our Universe actually does expand. An international team led by the Max Planck Institute for Astrophysics (MPA) has now used two gravitational lenses as new tools to calibrate the distances to hundreds of observed supernovae and thus measure a fairly high value for the Hubble constant. While the uncertainty is still relatively large, this is higher than that inferred from the cosmic microwave background. more

Recent high-resolution microwave and X-ray observations of the galaxy cluster RX J1347-1145 offer a new diagnosis tool of gas motion. Probing different parameters of the hot gas in galaxy clusters, these observations allow the MPA scientists to distinguish between gentle and violent motion of gas stirred by encounters with smaller sub-clusters. 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

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