The IMACS instrument will be well suited to studies of galaxy evolution, in particular, the detection, photometry, and spectroscopy of faint galaxies at high redshift. For example, the southern Hubble Deep Field (and flanking regions) will be available for studies of the redshift and evolutionary state of galaxies with r < 25. Although the smaller aperture means that integration times of a factor of 2 longer will be necessary, the Magellan Imaging Spectrograph will produce comparable or better results to the Keck + LRIS in its ground-breaking study of the northern Hubble Deep Field, and other faint galaxy samples. The principal questions include: what is the earliest epoch of star formation? how did the presently observed metal abundances of galaxies evolve? when did galaxy-sized structures first emerge?
In order to follow up on the detection of strong evolution in the mid-infrared from IRAS, NASA is building WIRE Wide-Field Infrared Explorer, to detect 12-micron emission from faint galaxies, WIRE will provide a catalog of tens of thousands of exotic objects, including star-bursts and AGNs, for which imaging and spectroscopy with a telescope the size of Magellan will be required (Hacking, 1996). The WIRE field size of 30' is an example of the importance of imaging and spectroscopy over as wide a field as possible, particularly in the study of exotic objects, for example, high redshift (z > 4) galaxies and quasars, and objects with strong infrared, x-ray, or radio emission. Because of its exceptionally wide-field coverage and versatility in terms of wavelength coverage and resolution, the Magellan Imaging Spectrograph will have applicability to a very broad range of programs relating to the early universe, galaxy formation and evolution, and the nature of exotic objects.