Detecting edges in the X-ray surface brightness of galaxy clusters
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Oxford University Press
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Sanders, J., Fabian, A., Russell, H., Walker, S., & Blundell, K. (2016). Detecting edges in the X-ray surface brightness of galaxy clusters. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 460 (2), 1898-1911. https://doi.org/10.1093/mnras/stw1119
The effects of many physical processes in the intracluster medium of galaxy clusters imprint themselves in X-ray surface brightness images. It is therefore important to choose optimal methods for extracting information from and enhancing the interpretability of such images. We describe in detail a gradient filtering edge detection method that we previously applied to images of the Centaurus cluster of galaxies. The Gaussian gradient filter measures the gradient in the surface brightness distribution on particular spatial scales. We apply this filter on different scales to Chandra X-ray observatory images of two clusters with active galactic nucleus feedback, the Perseus cluster and M 87, and a merging system, A 3667. By combining filtered images on different scales using radial filters spectacular images of the edges in a cluster are produced. We describe how to assess the significance of features in filtered images. We find the gradient filtering technique to have significant advantages for detecting many kinds of features compared to other analysis techniques, such as unsharp masking. Filtering cluster images in this way in a hard energy band allows shocks to be detected.
techniques: image processing, X-rays: galaxies: clusters
ACF, HRR and SAW acknowledge support from the ERC Advanced Grant FEEDBACK. The scientific results reported in this article are based on data obtained from the Chandra Data Archive.
External DOI: https://doi.org/10.1093/mnras/stw1119
This record's URL: https://www.repository.cam.ac.uk/handle/1810/263448