PANHIT SEDs of three selected models with ages < 0.3 Gyr (see text). The yellow line shows an old (0.29 Gyr), low-metallicity (Z = 0.0004) model (Low Z), the pink line shows a model with the same age but high metallicity (Z = 0.02 ; High Z) and the blue line shows a young, low-metallicity model (Young; Age = 2 Myr, Z = 0.0001). The main panel shows the spectrum in the rest-frame UV and optical, with upper limits and measured photometry from HST and VLT/HAWK-I. The small panels show our ALMA upper limits on the dust continuum (top panel) and the [O III] emission line (bottom panel). Upper limits are at the 3σ level and are indicated with arrows. We note that the dust-continuum fluxes of the three models (crosses) overlap in the top panel.