While progress on high redshift galaxies has been quite dramatic over the last few years a number of changes are underway that will provide a similar quantum step in capability in just the next 4-5 years. The new facilities and instruments can be put into three groups.
Large Ground-Based Telescopes: - there will be roughly an order-of-magnitude increase in the number of large ground-based telescopes, from the two Keck 10-m telescopes, as the four ESO VLT 8-m telescopes are commissioned and a further 8-10 large ( 6.5 m) O/IR telescopes become operational (the ~ 16 are evenly split N and S). These will have efficient optical and near-IR (~ 1-2 µm) imagers, and multiobject spectrographs, such as DEIMOS (for Keck) and NIRMOS and VIRMOS (for the VLT), giving large throughput gains. The potential of adaptive optics for studying distant galaxies is substantial, and is part of the focus of a major new adaptive optics center funded by the NSF at the University of California, Santa Cruz - the Center for Adaptive Optics (CfAO).
Hubble Space Telescope: - there will be substantial increase in HST's capabilities, through the development of new imagers - the typical gains over current instrumentation are > 10X. These instruments include the wide-field CCD Advanced Camera with its SDSS filter set (as well as a large complement of narrow-band and other broad-band filters). The ACS will be launched on the HST servicing mission SM-3B in 2001. The WFC3/IR UV-IR imager that adds wide-field IR imaging capability in J and H to HST is slated for launch on the HST servicing mission SM-4 in 2004.
Submm/IR: - there will also be major developments in submm imaging, starting with upgraded SCUBA-like imagers on the JCMT, and followed by new interferometer arrays, particularly ALMA, the Atacama Large Millimeter Array. ALMA will be an extremely powerful facility for studying dusty objects over a large range of redshifts. Ultimately, NGST should allow us to directly image extremely young protogalaxies during their first major star forming events.
The key to characterizing the universe at intermediate (z ~ 1) and high (z ~ 3-5+) redshifts, and beyond, will be through extensive surveys to very weak flux levels. Such combined redshift and imaging surveys (e.g., DEEP - see Davis and Faber 1999; Koo 1999) should produce samples with a level of statistical robustness that will be unheralded for distant galaxies.