The H2 density within spiral and irregular galaxies at high redshift: estimating CO detection limits

We have computed a grid of chemical evolution models for a large set of spiral and irregular theoretical galaxies of different total mass. In our models, the gas phase has two components, the diffuse and the molecular one (H2). It is possible, therefore, to follow the time (or redshift) evolution of the expected density of the H2 phase. We will show the predictions of this gas density at hight redshift, which might be detected with ALMA, in this type of galaxies.