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8. Concluding Remarks and Future Prospects

This is a very rapidly changing field of research. The advent of the 10m-class optical telescopes such as Keck, soon to be joined by others, has revolutionised our understanding of galaxy evolution in recent years and much still can be done in the optical and near-infrared: the recent discoveries of Lyman alpha emission from a few galaxies at z = 3-6 (Dey et al. 1998, Hu et al. 1998), shows that not all galaxies at this epoch are dusty, which provides fresh hope for the discovery of PGs when the new generation of even larger near-IR arrays becomes available on the largest telescopes. Certainly the US space agency NASA recognises the importance of continuing PG searches: over the next two decades it has dedicated itself to the ``cosmic origins'' programme, designed to answer such questions as ``how did the first galaxies form?''This will require a succession of sophisticated telescopes, each building on the results of previous missions augmented with ground-based observations. One such project is the New Generation Space Telescope - a 4m (or possibly 8m) descendant of the incumbent Hubble Space Telescope, designed for diffraction-limited imaging over 1 deg2. With such capability it will be possible to observe the individual supernovae explosions resulting from massive bursts of star formation happening at almost any epoch.

Undoubtedly, far-infrared and submillimetre observations will have future role to play in the unfolding story: the Planck satellite mission (named after the German physicist Max Planck), is part of the European Space Agency's Horizon 2000 Scientific Programme. Due to be launched in appeq 2005, Planck will survey the whole sky at millimetre wavelengths with unprecedented sensitivity and angular resolution. Designed primarilly to map fluctuations in the cosmic microwave background, Planck has the capability to detect small fluctuations in the far-infrared background tentatively detected by COBE, thereby distinguishing between rival theories predicting different epochs of galaxy formation. Perhaps the most exciting prospect on the timescale of 10 yrs or so, is the development of millimetre array imagers, capable of both high spatial and spectral resolution imaging over the whole sub-millimetre waveband. For example, the National Radio Astronomical Observatories millimetre array, proposed to the US National Science Foundation will provide a spatial resolution of 10 milliarcsec between 10 mm - 350 µm and a sensitivity capable of detecting the dust emission from a bright star-forming galaxy with luminosity > 1011 Lsmsun to z = 20.


I would like to thank Gordon Rogers for the spectral energy distribution plots and Doug Burke for useful discussions.

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