The X-ray Angular Power Spectrum of Extended Sources in the eROSITA Final Equatorial Depth Survey

Abstract

The eROSITA Final Equatorial Depth Survey (eFEDS), with a sky area of 140 square degrees with depth equivalent to the equatorial patch of the final eROSITA all-sky survey, represents the largest continuous non full-sky X-ray fields to-date, making it the premier dataset for measuring the angular power spectrum. In this work, we measure the X-ray angular power spectrum of galaxy clusters and groups in the eFEDS field. We show that the measured power spectrum at large angular scales (multipole ℓ < 2000) is consistent with that of the ROSAT All Sky Survey, as well as the predictions of cluster gas halo model that is calibrated from Chandra observations of galaxy clusters. At small angular scales (ℓ > 2000) , the eFEDS power spectrum is around an order of magnitude higher than the power spectrum of the Chandra/COSMOS field, and the halo model prediction. A follow-up of the impact of point source contamination with the higher angular resolution instruments like Chandra will resolve this tension. If we restrict the angular scales where eFEDS power agrees with observations and model predictions, we show that the X-ray power spectrum from the upcoming eROSITA all sky data can achieve percent-level constraints on Ω 𝑀 and 𝜎8, which are competitive to other cosmological probes.