Star Formation and Molecular Gas in the First Three Billion Years

Thu, April 16, 2015

In the first few Gyr of cosmic history, the bulk of the stellar mass was assembled under conditions of higher density and lower metallicity than we observe locally. While the most advanced optical/IR facilities have provided very detailed studies of galaxies at z~2-5 and detections of rare galaxies at in the epoch of reionization, it continues to be extremely difficult to study the cool phase of the ISM from which their stars arise. Understanding this cool phase, and the star formation that it obscures, is crucial to improving our picture of galaxy formation. I will report on two different views of the cool ISM in the early universe. First, millimeter and submillimeter facilities have provided new samples of gravitationally lensed starburst galaxies at z>3 that are exceptional targets for detailed study with ALMA. I will present the central findings of early-science ALMA studies of lensed galaxies identified in the South Pole Telescope survey. Second, star formation in the more common but less luminous galaxies that fill the early universe is much more challenging to observe, at least for individual galaxies. I will describe our efforts to study the development of the molecular ISM through intensity mapping, which measures fluctuations in the aggregate signal from distant galaxies. I will present first intensity mapping constraints at z~3 from a demonstration experiment, and discuss the prospects for pushing deeper.