Euclid view of the dusty star-forming galaxies at z ≳ 1.5 detected in wide area sub-millimetre surveys

We investigate the constraints provided by the Euclid space observatory on the physical properties of dusty star-forming galaxies (DSFGs) at z ≳ 1.5 detected in wide area sub-millimetre surveys with Herschel. We adopt a physical model for the high-z progenitors of spheroidal galaxies, which form the bulk of DSFGs at z ≳ 1.5. We improve the model by combining the output of the equations of the model with a formalism for the spectral energy distribution (SED). After optimising the SED parameters to reproduce the measured infrared luminosity function and number counts of DFSGs, we simulated a sample of DSFGs over 100 deg2 and then applied a 5 σ detection limit of 37 mJy at 250 μm. We estimated the redshifts from the Euclid data and then fitted the Euclid+Herschel photometry with the code CIGALE to extract the physical parameters. We found that $100\%$ of the Herschel galaxies are detected in all 4 Euclid bands above 3 σ. For $87\%$ of these sources the accuracy on 1 + z is better than 15%. The sample comprises mostly massive, i.e. log (M⋆/M⊙) ∼ 10.5 − 12.9, highly star–forming, i.e. log (SFR/M⊙yr−1) ∼ 1.5 − 4, dusty, i.e. log (Mdust/M⊙) ∼ 7.5 − 9.9, galaxies. The measured stellar masses have a dispersion of 0.19 dex around the true value, thus showing that Euclid will provide reliable stellar mass estimates for the majority of the bright DSFGs at z ≳ 1.5 detected by Herschel. We also explored the effect of complementing the Euclid photometry with that from the Vera C. Rubin Observatory/LSST.