The X-ray Angular Power Spectrum of Extended Sources in the eROSITA
  Final Equatorial Depth Survey
  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 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, 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 $\Omega_M$ and $\sigma8$,
which are competitive to other cosmological probes.
