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

Teaser 1503316854

Probing molecular clouds with supermassive black hole X-ray flares

September 01, 2017
The centre of the Milky Way is a very special place, harboring many exotic objects, such as the supermassive black hole Sagittarius A* and giant molecular clouds. Some of these clouds, despite being cold, are sources of high energy photons. It is believed that the clouds are not producing these photons themselves, but rather scatter the X-ray radiation coming from outside.  Even though Sgr A* is currently very faint in X-rays, it is considered as the main culprit of this radiation, in the form of short but intense flares, which happened over the past few hundred years. The time delay caused by light propagation from Sgr A* to the clouds and then to us, allows one to study Sgr A*’s past activity. At the same time, flares serve as an extremely powerful probe of molecular gas properties. In particular, the full 3D structure of molecular clouds and their density distribution on small scales can be reconstructed. [more]
Teaser 1500988871

Instabilities in relativistic magnetized accretion disks

August 01, 2017
Using three-dimensional general relativistic magnetohydrodynamic simulations, scientists at the Max Planck Institute for Astrophysics (MPA) have studied thick accretion disks orbiting around black holes. They find that weak magnetic fields can suppress the development of large-scale over-densities in the accretion flow. The onset of magnetic turbulence reshapes the disk's structure and could even quench the gravitational-wave signal produced by the accreting torus without magnetic fields. [more]
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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]
Teaser 1496163254

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]
Teaser 1490884776

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]
Teaser image horizontal 1487931538

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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