Gas dynamics across cosmic time

The emission lines of cold/warm gas are key tools to trace galaxy dynamics at different cosmic epochs. At z=0, the combination of Hα, CO, and HI observations allowed studying gas dynamics in hundreds of galaxies of different masses and morphologies, from quiescent ellipticals to star-forming dwarf irregulars. Regular rotation and low gas turbulence are the rule at z=0 with the exception of interacting and merging systems. Combined Hα+HI rotation curves extend from the innermost regions of galaxies out to tens of effective radii, probing deep into their dark matter halos. These data revealed surprisingly tight scaling relations between baryons and dark matter, which challenge current models of galaxy formation. At z=1-3, integral-field spectroscopy of Hα and [OIII]5007 Å lines allowed tracing the inner dynamics of massive galaxies for significant samples: the importance of disk turbulence, the rotation-curve shapes, and the evolution of scaling relations remain debated at this cosmic epoch. Radio and sub-mm interferometry of CO and [CI] lines are also key tools at z=1-3 albeit currently limited to small galaxy samples. At z=4-7, ALMA observations of the [CII]-158 μm line have opened anm line have opened an entirely new window for galaxy dynamics. The study of the high-z Universe is particularly promising to test the predictions of current models of galaxy formation.