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Observational evidence of cosmic magnetic fields in a galaxy cluster.

If the authors’ interpretation is correct, it is a remarkable finding, because it implies that relatively strong, ordered magnetic fields (of a few tens of microgauss in strength) exist in the highly disrupted environments of galaxy clusters such as Abell 3376. For comparison, relatively weak magnetic fields (of a few microgauss) have been detected¹³ in the gas at the centres of clusters less disrupted than Abell 3376. So far, it has proved extremely challenging to detect and measure magnetic fields in clusters and in the space between galaxies, and the origin of cosmic magnetic fields is still mysterious. Consequently, any observational evidence for such fields in cluster environments is valuable.

However, there is another plausible explanation for the bent jets, referred to as the slingshot model. In this scenario, MRC 0600‑399 and the nearby radio galaxy are falling back towards the centre of Abell 3376 after being ejected from the centre at supersonic speed. The radio jets of MRC 0600‑399 are bent simply by the pressure of gaseous wind acting in the opposite direction to the galaxy’s motion. Although this alternative model can explain the bent jets, it cannot account for the peculiar double-scythe structures, which suggest that the jets are interacting with a layer of strong, ordered magnetic fields. One limitation of the current work is that the magnetic-field strength in the jet-interaction region was not measured directly but was obtained from numerical simulations.

Continue reading “Black hole jets bent by magnetic fields” »

New observations and simulations show that jets of high-energy particles emitted from the central massive black hole in the brightest galaxy in galaxy clusters can be used to map the structure of invisible inter-cluster magnetic fields. These findings provide astronomers with a new tool for investigating previously unexplored aspects of clusters of galaxies.

As clusters of galaxies grow through collisions with surrounding matter, they create bow shocks and wakes in their dilute plasma. The plasma motion induced by these activities can drape intra–cluster magnetic layers, forming virtual walls of magnetic force. These magnetic layers, however, can only be observed indirectly when something interacts with them. Because it is simply difficult to identify such interactions, the nature of intra-cluster magnetic fields remains poorly understood. A new approach to map/characterize magnetic layers is highly desired.

An international team of astronomers including Haruka Sakemi, a graduate student at Kyushu University (now a research fellow at the National Astronomical Observatory of Japan—NAOJ), used the MeerKAT radio telescope located in the Northern Karoo desert of South Africa to observe a bright galaxy in the merging galaxy cluster Abell 3376 known as MRC 0600–399. Located more than 600 million light-years away in the direction of the constellation Columba, MRC 0600–399 is known to have unusual jet structures bent to 90-degree angles. Previous X-ray observations revealed that MRC 0600–399 is the core of a sub-cluster penetrating the main cluster of galaxies, indicating the presence of strong magnetic layers at the boundary between the main and sub-clusters. These features make MRC 0600–399 an ideal laboratory to investigate interactions between jets and strong magnetic layers.

Scientists are certain that dark matter exists. Yet, after more than 50 years of searching, they still have no direct evidence for the mysterious substance.

University of Delaware’s Swati Singh is among a small group of researchers across the dark matter community that have begun to wonder if they are looking for the right type of dark matter.

Continue reading “Researchers propose repurposing tabletop sensors to search for dark matter” »

Astronomers are hoping to use the wake of stars to test the existing theories of dark matter.

The detection of the axion would mark a key episode in the history of science. This hypothetical particle could resolve two fundamental problems of Modern Physics at the same time: the problem of Charge and Parity in the strong interaction, and the mystery of dark matter. However, in spite of the high scientific interest in finding it, the search at high radio frequency-above 6 GHz-has been almost left aside for the lack of the high sensitivity technology which could be built at reasonable cost. Until now.

The Instituto de Astrofísica de Canarias (IAC) will participate in an international collaboration to develop the DALI (Dark-photons & Axion-Like particles Interferometer) experiment, an astro-particle telescope for dark matter whose scientific objective is the search for axions and paraphotons in the 6 to 60 GHz band. The prototype, proof of concept, is currently in the design and fabrication phase at the IAC. The white-paper describing the experiment has been accepted for publication in the Journal of Cosmology and Astroparticle Physics (JCAP).

Predicted by theory in the 1970’s, the axion is a hypothetical low mass particle that interacts weakly with standard particles such as nucleons and electrons, as well as with photons. These proposed interactions are studied to try to detect the axion with different types of instruments. One promising technique is to study the interaction of axions with standard photons.

The extended Baryon Oscillation Spectroscopic Survey (eBOSS) collaboration has released its latest scientific results. These results include two studies on dark energy led by Prof. ZHAO Gongbo and Prof. WANG Yuting, respectively, from National Astronomical Observatories of the Chinese Academy of Sciences(NAOC).

The study led by Prof. Zhao was recently published in Monthly Notices of the Royal Astronomical Society.

Based on eBOSS observations, Prof. ZHAO’s team measured the history of cosmic expansion and structure growth in a huge volume of the past universe, corresponding to a distance range between 0.7 and 1.8 billion light years away from us. This volume had never been probed before.

Some are blasted out of galaxies by interactions with black holes; others, which orbit supermassive black holes, can smash together in titanic explosions.

Circa 2018

An elusive substance that permeates the universe exerts many detectable gravitational influences yet eludes direct detection.

Circa 2018 o.o

In 2018 an international team of researchers using the NASA/ESA Hubble Space Telescope and several other observatories uncovered, for the first time, a galaxy in our cosmic neighborhood that is missing most of its dark matter.