L_X-SFR distribution of the HEC-eR1 star-forming galaxies with reliable flux measurement colour-coded with the log($f_{\mathrm{Edd}}^{\mathrm{bol}}$), computed under the assumption that the observed X-ray luminosity is produced by accretion onto a nuclear SMBH. Galaxies in the black circles belong to the most extreme X-ray luminous galaxies of our sample for which we have available SDSS spectra.