Daily Image
23-06-2010
LOFAR image of Abell 2256
| Submitter: | Reinout van Weeren |
| Description: | Galaxy clusters are the largest gravitationally bound objects in the universe. These clusters also contain a large amount of hot gas which emits at X-ray wavelengths. Galaxy clusters grow by mergers with other clusters and galaxy groups. During a merger event large shock waves are created which heat the gas in the cluster. It is thought that within these shocks particles are accelerated to highly relativistic energies. In the presence of a magnetic field these particles will emit synchrotron radiation visible at radio wavelengths. It has been suggested that such synchrotron emitting regions can be identified with so-called radio relics - diffuse, steep spectrum, radio sources found in some clusters. Besides radio relics, some clusters also contain a diffuse radio halo. Radio halos could be the result of turbulence in the hot gas, caused by a cluster merger event. A textbook example of a cluster hosting a radio relic and halo is Abell 2256. This cluster was observed with LOFAR in the HBA band (115-165 MHz) in May 2010 for about 8 hours. The data were taken with 10 core stations and 5 remote stations (the core stations were split resulting in a total of 25 stations). The image was made using 18 subbands covering a total of 4 MHz of bandwidth around 135 MHz. The resolution of the image is 25 arcsec and the noise is a few mJy/beam, making it already one of the deepest images ever obtained of this cluster at low-frequencies. The next step will be to combine all 240 available subbands to create an ever deeper image. The yellow (brighter) regions in the image are associated with several disturbed radio galaxies. The large-scale emission in red and blue is mostly from the radio relic, although some additional faint emission in the south of the cluster (bottom of the image) comes from the radio halo. Data processing by: R. van Weeren, A. Bonafede, C. Ferrari, E. Orrų, R. Pizzo, A. Shulevski, S. van der Tol, and G. Macario. |
| Copyright: | LOFAR / Sterrewacht Leiden |
| Tweet |  |