These figures display the spectrum and best-fit power-law model for each source in the eFEDS main catalog, as discribed in Liu et al. 2021 (https://ui.adsabs.harvard.edu/abs/2021arXiv210614522L/abstract; Fig.6, left panel).
Since most of the eFEDS X-ray sources are AGN, we extracted the spectra assuming all the sources are unresolved, which is not true for (a few hundred of) galaxy clusters, and fitted the spectra with an absorbed power-law model, which is appropriate for AGN but not for stars or galaxy clusters. More details about the spectral modeling are given in Liu et al. 2021.
In the figure, the data (dark blue points) are rebinned for representation to reach a S/N of 3 but allowing at most 6 adjacent bins (each bin includes 4 channels) to be grouped. The blue solid, dashed, and dot-dashed lines display the best-fit model folded with the instrument responses, the folded best-fit source model, and the best-fit background model rescaled to the source extraction region, respectively. The shaded region indicate the 99% percentile condence interval of the model around the median. The lower panel compares the data with the best-fit model in terms of (data-model)/error, where error is calculated as the square root of the model predicted number of counts.