Currently, I am working on the new frontier for exploring and dissolving the Cosmic X-ray Background (CXB) via angular correlation studies with Chandra and XMM-Newton surveys. Our pioneering study with XBOOTES obtained some challenging results (Kolodzig et al. 2015, in prep.). We measure a strong clustering signal (excess), which no current clustering model of any major X-ray source population is able to explain. One of my current goals is to understand the origin of this excess by 1) improving our observational constrains via various methods, such as a) using large X-ray surveys from different instruments and at different depths and b) using cross-correlation with surveys at wavelength bands, and by 2) using simulations in order to test for instrumental and selection effects, and novel clustering models.
Previously, I have studied the prospects of using the 3 million AGN to be detected by the upcoming eROSITA all-sky survey (eRASS) for large-scale structure (LSS) studies (Kolodzig et al. 2013a,b). We show that it will be possible for the first time to perform detailed redshift- and luminosity-resolved studies of the clustering strength of X-ray selected AGN. Further, we are the first to demonstrate that the eRASS-AGN sample will enable us to convincingly detect baryon acoustic oscillations (BAOs) in the yet uncharted redshift range of z = 1 − 2. In an expansion of our work (Hütsi et al. 2014), we have performed a feasibility study for an optimal survey strategy with current and future X-ray telescopes in order to detect BAOs with X-ray-selected AGN.
