Example galaxy SEDs of stellar populations with different star formation histories. The star formation rate (see inset) rises linearly towards the present (right), with an exponential cutoff timescale τ. At low τ, the yellow SFR curve truncates quickly, indicating it is dominated by old stars. The corresponding yellow SED in the main panel peaks between 0.3 − 3 μm. The blue curve in the inset corresponds to continuously rising star formation. The corresponding blue SED in the main panel is dominated by luminous young stars, nebular emission lines and infrared dust emission. Minimal attenuation, E(B − V)=0.01, is applied.