Cold gas dynamics in high-z galaxies
Abstract
Gas dynamics play a key role in our understanding of the formation and evolution of galaxies. At z=0 gas dynamics has been extensively studied using a variety of tracers, such as the emission lines of atomic gas (HI), molecular gas (CO), and ionized gas (H-alpha). At high z, the study of galaxy dynamics has been largely restricted to warm ionized gas using the H-alpha and/or [OIII] lines, leading to a general picture in which high-z galaxies are more « clumpy » and turbulent than local ones. During the past few years, however, ALMA allowed us to study galaxy dynamics at z>1 using cold gas traces too, such as CO, [CI] and [CII] lines.
In this talk, I will discuss several in-depth studies of individual galaxies at z=1-6 with high-resolution ALMA data. The ALMA observations paint a new picture of galaxy dynamics at high z: the cold gas has a relatively smooth distribution and forms low-turbulence rotation-supported disks. In most cases, the inner rotation curve of the galaxy requires the presence of a central mass concentration in addition to a pure exponential disk (e.g., a stellar bulge). The existence of rotation-supported gas disks and stellar bulges at high z suggest that massive galaxies must have formed and evolved surprisingly fast during the first billion years of the Universe’s lifetime.