The Principal Investigator and collaborators in this project will combine three sophisticated computer codes in order to simulate the properties of galaxies at redshifts around 2 (approximately 10 billion years ago). These codes are (1) Arepo, an unstructured-adaptive-mesh hydrodynamics code based on Voronoi tessellations; (2) Sunrise, a Monte Carlo radiative transfer code that calculates spectral energy distributions from ultraviolet to millimeter wavelengths for galaxies with stellar and nonthermal sources modulated by scattering and absorption; and (3) Turtlebeach, a similar radiative transfer code that calculates molecular spectral line emission. The team will use these coupled codes to create a library of hydrodynamic simulations of isolated, evolving, and merging galaxies. They will then fold the resulting models through estimates of cosmological merger rates and merging histories obtained through semi-analytic and numerical methods. This strategy will make it possible to connect physical mechanisms operating on scales of tens of parsecs to observations from large-scale galaxy surveys. The goals of the project are (1) to construct a physically motivated unified model for the diverse "zoo" of high redshift galaxies, including galaxy populations expected to be discovered in deep surveys by the Atacama Large Millimeter Array, the James Webb Space Telescope, and the Herschel Space Telescope; (2) to assess the cosmological significance of the various high redshift galaxy populations, and determine the dominant contributors to cosmic stellar mass assembly and the far infrared background; and (3) to develop tools for observers based on a physical understanding of high-redshift galaxies and a critical assessment of the applicability of locally-calibrated diagnostics. The project will support a postdoctoral researcher and a graduate student, who will be mentored and trained by the Principal Investigator. The proposers will make public for the community expected luminosity functions for ALMA, JWST and Herschel deep fields in advance of these surveys. They will also conduct a series of 1-hour lectures as part of a continuing education program for senior citizens.