Program: GS-2004A-SV-7

We propose to constrain the star formation activity, dust reddening and metallicity of massive star-forming galaxies in the redshift desert (z~1.5) using the combination of UV luminosities and IR nebular emission lines. As part of the Gemini Deep Deep Survey (GDDS), we obtained UV spectra of massive galaxies in the very interesting (but very observationally challenging) 1 < z < 2 redshift range. As these galaxies are generally optically bright, lower star formation rates than in UV-selected Lyman-break galaxies can be measured. We propose GNIRS follow-up observations to measure [OIII], Hbeta and Halpha emission lines in 4 of massive starforming galaxies. The first investigated properties of similar GDDS galaxies show the qualitative differences between these objects and LBGs, being more massive, less star-forming and redder. Our preliminary study of the cold ISM in a subsample of GDDS galaxies revealed a significant enrichment of heavy elements. GNIRS observations are needed to test the accuracy of these results. Moreover, the Balmer decrement, given by Halpha/Hbeta, will provide a very accurate estimate of dust reddening. This will tell us whether metal-rich and massive galaxies at high redshift are hard to observe because they are rare, or because of observational biases related to dust reddening.