The Landscape of Large Sky Surveys in the Athena Era (Synergy Talk)

The transformation of astronomical research by the exponential growth of large sky surveys will be well advanced by the time of the Athena launch in 2028. At that point, e.g., the Large Synoptic Survey Telescope (LSST) should be more than halfway through its 10-year survey, and 2-3 additional generations of innovative smaller-scale projects will likely have been implemented. I will briefly describe the expected landscape of large sky surveys relevant to Athena, considering both ground-based (e.g., LSST, HSC, PS4, ZTF, LoFAR, ASKAP, MeerKAT, SKA, CTA, LIGO/VIRGO) and space-based (e.g., eROSITA, JWST, Euclid, WFIRST, HDST) projects. These will provide the essential multiwavelength data needed to execute some of Athena's central science goals, such as investigating the build-up of the first massive black holes. They will provide a plethora of exciting new targets for Athena spectroscopy, such as luminous quasars at z = 7-10 and high-redshift protoclusters. These surveys will (more than) fully exercise Athena's agility withthousands of nightly transients discovered across the entire sky.