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All News

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Simulating separate universes to study the clustering of dark matter

April 01, 2017
In the standard cosmological model, dark matter makes up roughly 25 % of the total energy budget of the Universe. However it cannot be observed directly, since it does not emit light. Understanding the way dark matter clusters together and forms structures is of crucial importance since it would help our understanding of the observed spatial distribution of galaxies (which should closely follow the dark matter distribution) and link this with early-Universe physics and the origin of initial perturbations. In this context, researchers at MPA and in other institutions worldwide came up with a new way of simulating the impact of large-scale primordial perturbations on the abundance of structures observed at late times, the so-called separate universe simulations. Using this technique, the MPA researchers recently obtained some of the most precise measurements of the local bias, confirming the known trend that more massive halos are more biased than smaller halos. [more]
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ALMA’s ability to see a “cosmic hole” confirmed

March 17, 2017
Researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) successfully imaged a radio “hole” around a galaxy cluster 4.8 billion light-years away. This is the highest resolution image ever taken of such a hole caused by the Sunyaev-Zel'dovich effect (SZ effect). The image proves ALMA’s high capability to investigate the distribution and temperature of gas around galaxy clusters through the SZ effect. [more]
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The Circum-galactic Medium of Galaxies as Probe of Gas Accretion

March 01, 2017
In collaboration with researchers from the USA, MPA scientists have mounted a series of ambitious experiments that use a combination of quasar absorption-line spectra, neutral hydrogen line data, and state-of-the-art cosmological hydrodynamical simulations to probe the interface between galaxies and their surrounding gaseous environment. The researchers found that galaxies with gas-rich disks are embedded within gas-rich halos and that the gas in these halos is distributed smoothly and relatively isotropically. [more]
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Probing the nature of the most luminous explosions

February 15, 2017
Supernovae are extremely bright stellar explosions – superluminous supernovae are even brighter. However, the nature of these most luminous explosions has remained a mystery. In a new study, MPA researchers now present their simulations of superluminous supernova spectra months and even years after the outbreak and show that they are very similar to gamma-ray bursts, another type of highly energetic explosions. In addition, the results point to very high masses of oxygen and magnesium, suggesting very massive progenitor stars that will use an exotic explosion mechanism rather than the standard neutrino-driven explosion believed to power most supernovae. [more]
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Constraining theories of gravity using the large-scale distribution of galaxies

February 01, 2017
The origin of the current accelerated expansion of the Universe remains one of the major unsolved mysteries in physics today. While this could be a sign of the mysterious “Dark Energy”, this puzzling observation might also be evidence for the inadequacy of Einstein’s theory of General Relativity (GR) to describe the law of gravity on very large cosmological scales. These considerations would have strong implications on our understanding of fundamental physics, warranting dedicated studies such as the one undertaken recently by researchers at MPA and MPE. In this work, the authors created mock universes with non-GR theories of gravity to test the validity of current observational methods to determine the rate at which structures grow in the Universe. This allowed them to place bounds on how much the current data allows the Universe to depart from Einstein’s prediction. Reassuringly, current observational methods do not show evidence for a biased performance when tested on mock universes with modified gravity. [more]
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Cosmic lenses support finding on faster than expected expansion of the Universe

January 26, 2017
By using galaxies as giant gravitational lenses, an international group of astronomers including researchers at the Max Planck Institute for Astrophysics have made an independent measurement of how fast the Universe is expanding. The newly measured expansion rate for the local Universe is consistent with earlier findings. These are, however, in intriguing disagreement with measurements of the early Universe. This hints at a fundamental problem at the very heart of our understanding of the cosmos. [more]
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Obituary to Heinz Billing

January 10, 2017
A pioneer in the development of electronic computing machines in Germany and one of the founders of gravitational wave astronomy is gone: on 4 January 2017, the astrophysicist Heinz Billing died at the age of 102. Billing was scientific member at the Max Planck Institute for Astrophysics in Garching from 1961 to '82. [more]
 
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