Figuring Out Gas & Galaxies in Enzo (FOGGIE). II. Emission from the z=3 Circumgalactic Medium

Observing the circumgalactic medium (CGM) in emission provides 3D maps of the spatial and kinematic extent of the gas that fuels galaxies and receives their feedback. We present mock emission-line maps of highly resolved CGM gas from the Figuring Out Gas & Galaxies in Enzo (FOGGIE) project and link these maps back to physical and spatial properties of the gas. In particular, we examine the ionization source leading to most O vi emission and how resolution affects the physical properties of the gas generating the emission. Finally, when increasing the spatial resolution alone, the total luminosity of the line emission increases by an order of magnitude for some lines considered. Current integral field unit instruments like Keck Cosmic Web Imager and Multi Unit Spectroscopic Explorer should be able to detect the brightest knots and filaments of such emission, and use this to infer the bulk kinematics of the CGM gas with respect to the galaxy. We conclude that the spatial resolution of simulated CGM gas can significantly influence the distribution of gas temperatures, densities, and metallicities that contribute to a given observable region. Greater spatial resolution than has been typically included in cosmological simulations to date is needed to properly interpret observations in terms of the underlying gas structure driving emission.