Research Highlights

On this page you can find a monthly updated list of short articles highlighting current MPA research topics.

Current Research Highlights

Current Research Highlights

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Wanted: the rotating radio emission of the Milky Way

July 01, 2017
The magnetic fields of the Milky Way cause electrons with nearly the speed of light to rotate and to emit radio waves. As consequence, this radiation should also "rotate" slightly, it is circularly polarized. This very weak circular polarization of the Milky Way, however, has not been observed so far. Researchers at the Max Planck Institute for Astrophysics and colleagues have now predicted some properties of this polarization and created a "wanted poster" to allow targeted searches. A measurement of the circular polarization would provide important insights into the structure of the galactic magnetic fields and confirm that electrons - and not positrons - are the source of this radio emission in the Milky Way. [more]
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Intense radiation and winds emitted by massive stars regulate star formation in galaxies

June 01, 2017
Only a small fraction of the stars that form in the Milky Way are much more massive than our Sun and explode as supernovae type II at the end of their lifetimes. Still, these high-mass stars influence the surrounding interstellar medium (ISM) much more than their small number might suggest, both by their intense radiation and powerful winds (“pre-supernova feedback”) and through their violent supernova explosions (“supernova feedback”). Scientists at the Max Planck Institute for Astrophysics, in the framework of the SILCC collaboration, use complex supercomputer simulations to investigate the detailed impact of the different feedback processes on the ISM with conditions similar to our solar neighborhood. Ionizing radiation from young, massive stars dominates their energy output and can exceed the energy released during supernova explosions by an order of magnitude. Only if the simulation includes this radiative feedback and the momentum input from stellar winds are the results consistent with observations of the ISM and the star formation rate is reduced. [more]
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“Gravitational noise” interferes with determining the coordinates of distant sources

May 01, 2017
It is widely known that our planet Earth and the Solar System itself are embedded in the Milky Way, and it is through this galaxy that we look out onto the Universe. As it turns out, this has a larger impact on astrophysical studies than previously thought. Our Galaxy’s gravitational field and its non-uniformity limit the accuracy of astrometric observations of distant – extragalactic – objects. An international group of astrophysicists including a researcher at the Max Planck Institute for Astrophysics tried to find out how strong this effect is. [more]
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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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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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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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The Hydrangea project: high-resolution hydrodynamic simulations of galaxy clusters

January 01, 2017
Why do galaxies that live in the enormous structures known as galaxy clusters look different from normal, isolated galaxies, such as our Milky Way? To answer this question, an international research team led by MPA has created the Hydrangea simulations, a suite of 24 high-resolution cosmological hydrodynamic simulations of galaxy clusters. Containing over 20,000 cluster galaxies in unprecedented detail and accuracy, these simulations provide astrophysicists with a powerful tool to understand how galaxies have formed and evolved in one of the most extreme environments of our Universe. [more]
 
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