Astronomers using the Karl G. Jansky Very Large Array (VLA) have captured the most detailed image yet of the merging cluster Abell 2256.
This VLA radio image shows the galaxy cluster Abell 2256. Image credit: Owen et al. / NRAO / AUI / NSF.
Abell 2256 is a cluster of galaxies, located at a distance of about 800 million light-years, in the constellation Ursa Minor.
The cluster contains over 500 galaxies, with the elliptical galaxy NGC 6331 as the brightest at magnitude 12.8.
Studied by astronomers for more than half a century with telescopes ranging from radio to X-ray, Abell 2256 has a radio halo, relic and several head-tail sources, and is some 4 million light-years across.
The new image from the Karl G. Jansky Very Large Array shows the cluster as it would appear if human eyes were sensitive to radio waves instead of light waves.
In this image, red shows where longer radio waves predominate, and blue shows where shorter radio waves predominate, following the pattern we see in visible light.
The image shows a number of strange features the astronomers think are related to an ongoing collision of galaxy clusters. It covers an area in the sky almost as large as the full moon.
“With monikers such as ‘Large Relic,’ ‘Halo,’ and ‘Long Tail,’ the features in this region are seen in greater fidelity than ever before,” said Dr Frazer Owen from the National Radio Astronomy Observatory, the first author of the paper accepted for publication in the Astrophysical Journal (arXiv.org preprint).
“The image reveals details of the interactions between the two merging clusters and suggests that previously unexpected physical processes are at work in such encounters.”
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Frazer Owen et al. 2015. Wideband VLA Observations of Abell 2256 I: Continuum, Rotation Measure and Spectral Imaging. ApJ, accepted for publication; arXiv: 1408.5931
