ESO's XXL galaxy cluster survey could improve our understanding of dark matter
An international team of astronomershas used multiple telescopes to study two large patches of sky,searching for the X-ray emissions from distant galaxy clusters. It's hoped that the work will provide insights into thenature of dark matter and dark energy.
The XXL survey, which is one of thelargest ever of its kind, focuses on the most massive gravitationallybound structures in the Universe – galaxy clusters. These massiveobjects house reservoirs of gas with temperatures so high that theyemit X-rays that can be observed by telescopes orbiting Earth.Gaining a better understanding of these clusters is important, asit's believed that they are influenced by the most elusive componentsof the Universe – dark matter and dark energy.
The new survey was conducted by aninternational team of more than 100 astronomers, searching twopatches of sky, each around 100 times the size of the moon. The studyis making use of X-ray observations from the ESA's XMM-Newton orbiting space telescope alongside ground-based data frominstallations such as the ESO's Very Large Telescope (VLT) and New Technology Telescope (NTT), coming together to forma huge collection of data across the electromagnetic spectrum.
The XMM-Newton telescope was used toidentify the clusters, while the NTT and VLT focused on working outexactly how far away each object is. This two-fold method allowed theastronomers to build a three dimensional view of the clusters, whichin turns allows for the precise measurement and analysis of dark matter and dark energy.
At present, only one fifth of the totalexpected data has been processed, but several interesting discoverieshave already been made. These include the identification of five newgroups of galaxy clusters – each referred to as a supercluster –and evidence to support the notion that the observed galaxy clustersare scaled down versions of those seen in the modern Universe.
The findings also confirmed that thereare a lower number of clusters present in the early Universe thansuggested by predictive models based on observations by ESA's Plancktelescope. While the reason for this is currently unknown, the XXLsurvey team believes that the mystery will be solved once the fullsample data is available, which is expected in 2017.