Incorporating all the effects relevant to star formation into accurate simulations of the interstellar medium is a major frontier in astrophysics. These authors start to tackle the effects of chemical composition.
Water plays an important role in the inter-stellar medium, but getting good spectra for star forming cores is difficult. A radio technique exploiting masers allows these authors to probe water in Cep E.
Galaxies come in many different flavors, therefore models of galaxy formation and evolution must reconcile theory with what we observe. The issue addressed in this paper is that current semi-analytic models over predict the fraction of late-type satellite galaxies that are passive (not forming stars).
Studying galaxies at high redshift helps us to understand how galaxies formed and evolved; in particular, astronomers are interested in the rates of star formation in galaxies and how these rates change with time.