Left: spectra retrieved by GMCA for different thermal emission-to-synchrotron ratios with a total number of counts corresponding to a 1 Ms observation. Retrieved and theoretical spectra are shown in solid and dotted lines, respectively. The synchrotron spectrum is displayed as an indication of the relative strengths. Right: kT retrieved by Xspec by fitting a thermal model on the thermal emission spectra retrieved by GMCA for different Fe line-to-synchrotron ratios with a total number of counts corresponding to a 100 ks observation. For each ratio, we made a Monte-Carlo with 100 realizations, fitting in Xspec a thermal model on every realization associated with the error bars given by the Monte-Carlo. The theoretical kT is 2 keV and is indicated by the blue dotted line.