Research Highlights

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

Current Research Highlights

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Constraining the reionization history from Lyman alpha emitting galaxies

May 01, 2016
In cosmology, one of the major challenges in next decades will be probing the epoch of reionization in the early universe. Scientists at MPA, the University of Oslo, and INAF have now used cosmological hydrodynamical, radiative transfer simulations to understand the impact of the complex distribution of neutral gas in the intergalactic medium on distant galaxies. Combining the simulations with observations of so-called Lyman alpha emitting galaxies they find that despite the uncertainty, the current simulation-calibrated measurements favour a late and rapid reionization history. The study also emphasizes that both the large-scale distribution of ionised gas regions and the small-scale structures of the intergalactic gas around galaxies must be understood to derive more robust constraints on the reionization epoch. [more]
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Is Dark Matter the Source of a Mysterious X-ray Emission Line?

April 01, 2016
The nature of dark matter is still unknown, but one potential candidate is a theoretical particle known as the “sterile neutrino”. In 2014, two independent groups of astronomers detected an unknown X-ray emission line around an energy of 3.5 keV in stacked X-ray spectra of galaxy clusters and in the centre of the Andromeda galaxy. The properties of this emission line are consistent with many of the expectations for the decay of sterile neutrino dark matter. However, if this hypothesis is correct, all massive objects in the Universe should exhibit this spectral feature. To test this intriguing possibility, scientists at MPA and the University of Michigan examined two large samples of galaxies, finding no evidence for the line in their stacked galaxy spectra. This strongly suggests that the mysterious 3.5 keV emission line does not originate from decaying dark matter. The nature of dark matter, and the origin of this emission line, both remain unknown. [more]
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The DRAGON globular cluster simulations: a million stars, black holes and gravitational waves

March 01, 2016
An international team of experts from Europe and China has performed the first simulations of globular clusters with a million stars on the high-performance GPU cluster of the Max Planck Computing and Data Facility. These – up to now - largest and most realistic simulations can not only reproduce observed properties of stars in globular clusters at unprecedented detail but also shed light into the dark world of black holes. The computer models produce high quality synthetic data comparable to Hubble Space Telescope observations. They also predict nuclear clusters of single and binary black holes. The recently detected gravitational wave signal might have originated from a binary black hole merger in the center of a globular cluster. [more]
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Where are all of the nebulae ionized by supersoft X-ray sources?

February 01, 2016
The ultimate fate of low-mass stars, like our own Sun, is to exhaust the nuclear furnace in their cores, expel their extended atmospheres, and leave behind a hot remnant called a white dwarf. Left to their own devices, these objects will simply cool slowly over billions of years. However, if a white dwarf comes to accrete material from some stellar companion, it can become an incredibly luminous source of extreme UV and soft X-ray emission, a “supersoft X-ray source” or SSS. Such radiation is readily absorbed by any surrounding interstellar gas, producing emission line nebulae. Therefore, we would expect such nebulae to be found accompanying all supersoft X-ray sources. However, of all SSSs found in the past three decades, only one has been observed to have such a nebula. Clearly, something is amiss in our understanding of these incredible objects. Now, scientists at MPA and the Monash Centre for Astrophysics have pieced together the puzzle. [more]
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The diversity of stellar halos in massive disk galaxies

January 01, 2016
The stellar halos of galaxies are diffuse and faint components which provide scientists with a window into the assembling history of galaxies. A research team at MPA has investigated the properties of stellar halos in large disk galaxies by using both observations and state-of-the-art simulations of galaxy formation. They find a great diversity in the halo properties for galaxies that are – otherwise – alike in terms of morphology, mass, and luminosity. Observed properties, such as a mean metallicity as a function of galactocentric distance, can be reproduced by the simulations if they are analyzed in the same way as the data. [more]
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How supernova explosions shape the interstellar medium and drive galactic outflows

December 01, 2015
With complex hydrodynamical simulations scientists at MPA investigate the detailed impact of supernova explosions on the chemical composition and the thermodynamic properties of the interstellar medium and galactic outflows. [more]
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The Distribution of Atomic Hydrogen in Simulated Galaxies

November 01, 2015
In simulated galaxies of the hydrodynamical cosmological “EAGLE” simulation the distribution of atomic hydrogen agrees with observations in unprecedented detail. This success means that EAGLE can aid astrophysicists to better understand the processes shaping real galaxies, such as the origin of their atomic hydrogen. EAGLE is not quite perfect, however: the study also found that some simulated galaxies contain unphysically large holes in their atomic hydrogen discs, meaning further work for simulators to improve the models underlying the treatment of supernova explosions and the interstellar matter. [more]
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