The 365 galaxy clusters of the XXL Survey – Optical view
This mosaic shows the 365 galaxy clusters of the XXL Survey as imaged in optical wavelengths by the Canada-France-Hawaii Telescope and by the Blanco telescope at the Cerro Tololo Inter-American Observatory.
The clusters are ordered by increasing distance from us, starting from the most nearby, at a redshift of 0.03, in the top left corner, all the way to the most distant one, at a redshift of 1.99 (the seventeenth cluster in the bottom row from the left); the last seven clusters in the bottom row have uncertain redshift.
The XXL Survey is XMM-Newton's largest observational programme to date. The second batch of data from the survey includes information on 365 galaxy clusters, which trace the large-scale structure of the Universe and its evolution through time, and on 26 000 active galactic nuclei (AGN).