Stellar and gas emission spectra generated by stellar population model PEGASE. The solid lines show models with instantaneous star formation (with decreasing luminosity as age increases), while the dotted lines show models with constant star formation (with increasing luminosity as age increases). Here we normalize the instantaneous star formation models to ﹩1\,{M}_{\odot }﹩ and constant star formation models to ﹩1\,{M}_{\odot }/\mathrm{Myr}﹩. These models use solar metallicity and have gas emission (continuum and lines) added.