LOFAR and Radio Astronomy
The radio astronomy group at Hamburger Sternwarte is focused on extragalactic research using the LOFAR radio interferometer. In particular, we study the origin of diffuse radio emission in galaxy clusters. Among such sources are so-called radio relics and radio halos. They are produced by ultra-fast electrons in magnetic fields. Both, the origin of the fast electrons as well as the origin of the magnetic fields are not understood.
Using data from NASA's Chandra X-ray Observatory and several other telescopes, we have discovered a cosmic one-two punch unlike any ever seen in a pair of colliding galaxy clusters called Abell 3411 and Abell 3412. This result shows that an eruption from a supermassive black hole combined with a galaxy cluster merger can create a stupendous cosmic particle accelerator.
This composite image contains X-rays from Chandra (blue) that reveals diffuse emission from multi-million-degree gas in the two clusters. The comet-shaped appearance of the hot gas provides clear evidence that the two clusters are colliding and merging. The "head" of the comet is hot gas from one cluster plowing through the hot gas of the other cluster, in the direction shown by the arrow in the labeled image. Radio emission detected by the Giant Metrewave Radio Telescope in India (red) represents colossal shock waves — cosmic versions of sonic booms generated by supersonic aircraft — produced by the collision of the hot gas associated with the galaxy clusters. Optical data from the Subaru telescope atop Mauna Kea, Hawaii, shows galaxies and stars with a range of different colors. This new image also shows three different supermassive black holes in galaxies located in the merging clusters. The upper one shows that a jet powered by a supermassive black hole is connected to large swirls of radio emission. The team of astronomers thinks this connection provides important information about how the radio emission was produced.
Nature Astronomy 1, (2017)
The case for electron re-acceleration at galaxy cluster shocks / Van Weeren, Reinout J.; Andrade-Santos, Felipe; Dawson, William; Golovich, Nathan; Lal, Dharam V.; Kang, Hyesung; Ryu, Dongsu; Brüggen, Marcus; Ogrean, Georgiana; Forman, William R.; Jones, Christine; Placco, Vinicius; Santucci, Rafael; Wittman, David M.; Lee, M. James; Kraft, Ralph P.; Sobral, David; Stroe, Andra; Fogarty, Kevin
A giant galaxy
In this picture of the Abell A1132 we have discovered a giant radio galaxy that is more than 3 million light years long. It is seen in the red emission in the image below and was produced by PhD student Amanda Wilber using LOFAR and the GMRT radio telescopes.
Giant shock waves
In the picture, the galaxy cluster discovered by the Planck satellite, named PLCKG287.0 +32.9. Radio (Blue) X-ray (magenta) and optical emission are shown. The blue emission shows shock waves similar to supersonic booms - only that they stretch over a million light years. The picture is taken from Bonafede et al. (2014) published in the Astrophysical Journal.