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 FOGGIE project (Figuring Out Gas & Galaxies in Enzo) and link these maps back to physical and spatial properties of the gas. By increasing the spatial resolution alone, the total luminosity of the line emission increases by an order of magnitude. This increase arises in the abundance of dense small-scale structure resolved when the CGM gas is simulated to < 100 pc scales. Current integral field unit instruments like KCWI and MUSE should be able to detect the brightest knots and filaments of such emission, and from this to infer the bulk kinematics of the CGM gas with respect to the galaxy. We conclude that accounting for small-scale structure well below the level of instrument spatial resolution is necessary to properly interpret such observations in terms of the underlying gas structure driving observable emission.