Zusammenfassung
We combine a semi-analytic model of galaxy formation, which tracks atomic and
molecular phases of cold gas, with a three-dimensional radiative-transfer and
line tracing code to study the sub-mm emission from several atomic and
molecular species (CO, HCN, C, C+, OI) in galaxies. We aim to understand if
the physics that drives the formation of stars at the epoch of peak star
formation in the Universe is similar to or different from that in local
galaxies. We find that normal star-forming galaxies at high redshift have much
higher CO-excitation peaks than their local counterparts, higher HCN/CO ratios
and that CO cooling predominantly takes place through molecules with higher
excitation levels. We find an increase in the ratio between OI and CII in
typical star-forming galaxies at z = 1.2 and z = 2.0 with respect to
counterparts at z = 0. All our model results suggest that typical star-forming
galaxies at high redshift consist of much denser and warmer star-forming clouds
than their local counterparts and form their stars under significantly
different ISM conditions. Galaxies belonging to the tail of the SF activity
peak of the Universe (z = 1.2) are already less dense and cooler than
counterparts during the actual peak of SF activity (z = 2.0). We use our
results to discuss how future ALMA surveys can best confront our predictions
and constrain models of galaxy formation.
Nutzer