Predictions and Strategies for Integral-Field Spectroscopy of High-Redshift Galaxies

We investigate the ability of infrared integral-field spectrographs to map the velocity fields of high redshift galaxies, presenting a formalism which may be applied to any telescope and imaging spectrograph system. We discuss the 5-sigma limiting line fluxes which current integral-field spectrographs will reach, and extend this discussion to consider future large aperture telescopes with cryogenically cooled adaptive reimaging optics. In particular, we simulate observations of spectral line emission from star-forming regions at redshifts z = 0.5 to 2.5 using a variety of spatial sampling scales and give predictions for the signal-to-noise ratio expected as a function of redshift. Using values characteristic of the W.M. Keck II telescope and the new OH-Suppressing InfraRed Imaging Spectrograph (OSIRIS) we calculate integral-field signal-to-noise ratio maps for a sample of U_nGR color-selected star-forming galaxies at redshift z ~ 2 - 2.6 and demonstrate that OSIRIS will be able to reconstruct the two-dimensional projected velocity fields of these galaxies on scales of 100 mas (~ 1 kpc at redshift z ~ 2). With signal-to-noise ratios per spatial sample up to ~ 20, OSIRIS will in some cases be able to distinguish between merger activity and ordered disk rotation. Structures on scales smaller than 1 kpc may be detected by OSIRIS for particularly bright sources, and will be easy targets for future 30m class telescopes.