Line Intensity Mapping in the Far-Infrared: A New Technique for Connecting Galaxy Formation to Large-Scale Structure

Connecting the process of galaxy evolution to the overall growth of large-scale structure (LSS) must link the theoretical structure of dark matter halos to the masses, types, luminosities, star formation rates, and numbers of galaxies inhabiting them at any epoch. This requires studying scales from the interstellar medium (ISM) of galaxies up to the LSS.  Because the ISM in actively star-forming galaxies tends to have large quantities of dust, studying these processes is difficult in the visible and near infrared, which su ffer considerable extinction.

Further, mapping the clustering and environment of galaxies has typically required (optical) surveys of representative cosmic volumes with large spectroscopic or photometric redshift surveys.  In this talk I will discuss a powerful and potentially transformative new approach, line intensity mapping (LIM) using unextincted FIR lines diagnostic of the state of the ISM.  LIM uses a "data cube" containing the combined line emission from many individually unresolved galaxies to measure spatial variations in this emission across large regions of the Universe, primarily through the auto and cross spatial power spectra of the cube. This approach probes the properties of star forming gas over a range of large-scale environments, and nicely complements more traditional targeted observations of individual galaxies. I will discuss the LIM formalism, our predictions the likely strength and detectability of the LIM power spectrum of FIR lines for SPICA and a proposed balloon mission, and provide a guide for when line intensity mapping is to be preferred over traditional redshift surveys, and how it can complement them.