  The spectral energy distribution analysis of very young unresolved star
clusters challenges our understanding of the cluster formation process. Studies
of resolved massive clusters in the Milky Way and in the nearby Magellanic
Clouds show us that the contribution from photoionized gas is very important
during the first Myr of cluster evolution. We present our models which include
both a self-consistent treatment of the photoionized gas and the stellar
continuum and quantify the impact of such nebular component on the total flux
of young unresolved star clusters. A comparison with other available models is
considered. The very young star clusters in the SBS 0335-052E dwarf starburst
galaxy are used as a test for our models. Due to the low metallicity of the
galactic medium our models predict a longer lasted nebular phase which
contributes between 10-40% of the total near infrared (NIR) fluxes at around 10
Myr. We propose thus a possible solution for the observed flux excess in the 6
bright super star clusters of SBS 0335-052E. Reines et al. showed that the
observed cluster fluxes, in the red-optical and NIR range, sit irreconcilably
above the provided stellar continuum models. We find that in the age range
estimated from the H_alpha emission we can explain the red excess in all the 6
super star clusters as due to nebular emission, which at cluster ages around 10
Myr still affects the NIR wavebands substantially.

Cosmology and Nongalactic Astrophysics