Optical Spectra of Dusty Starbursts

This contribution presents the optical spectral properties of FIR-luminous galaxies, whose distinctive feature is often the simultaneous presence in the spectra of a strong $\rm H\delta$ line in absorption and of emission lines (e(a) spectra). A discrepancy between the star formation rate estimated from the FIR luminosity and that derived from the $\rm H\alpha$ luminosity persists even after having corrected the $\rm H\alpha$ flux for dust according to the observed Balmer decrement. It is shown that the e(a) spectrum can be reproduced assuming a current starburst and dust extinction affecting the youngest stellar populations much more than the older stars.