These are exciting times to be working on any aspect of studies of galaxies at high redshift whether observational or theoretical. Most would agree that the current period represents something of a golden era in the subject. Figure 1 shows the increasing extent to which articles concerned with galaxy evolution dominate the published literature over the past 25 years (gauged xenophobically I'm afraid by keyword statistics only in two North American journals).
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Figure 1. The remarkably rapid growth in galaxy evolution studies: the fraction of the ApJ and AJ literature containing the key word `galaxy evolution' over the past 25 years. The inset shows the marked decline in the use of galaxies as probes of the cosmological parameters during 1970-1980 (after Brinchmann, Ph.D. thesis 1998). |
To try and understand the cause for this prominence in the subject, the dates associated with the commissioning of some major observational facilities have been marked. The progress appears to have been driven largely by new kinds of optical and near-infrared data: faint counts and searches for primaeval galaxies in the late 1970's and early 1980's ([Peterson et al 1979, Tyson & Jarvis 1979, Kron 1980, Koo 1985]), faint galaxy redshift surveys made possible by multi-object spectrographs in the late 1980's and early 1990's ([Lilly et al 1995, Ellis et al 1996, Cowie et al 1996, Cohen et al 2000]), the launch of Hubble Space Telescope (HST) and its revelation of resolved galaxy images to significant redshifts ([Griffiths et al 1994, Glazebrook et al 1995, Brinchmann et al 1998]), the remarkable Hubble Deep Field image ([Williams et al 1996]) and the plethora of papers that followed ([Livio, Fall & Madau 1998]) and the arrival of the Keck telescopes bringing a new wave of faint Lyman-break galaxy spectroscopy at unprecedented redshifts ([Steidel et al 1996, Steidel et al 1999]) (2) .
One often hears claims that a subject undergoing spectacular progress is one that is nearing completion (c.f. [Horgan 1997]). After all, the rise in Figure 1 clearly cannot continue indefinitely and fairly soon, it could be argued, we will then have solved all of the essential problems in the subject. As if anticipating this, a theoretical colleague gave a recent colloquium at my institute entitled Galaxy Formation: End of the Road!
Consider the evidence. Observationally we may soon, via
photometric redshifts, have determined the redshift distribution,
luminosity evolution and spatial clustering of sources to
unprecedented limits. If one accepts photometric redshifts are
reliable, the rate of progress in the traditional pursuit of
N(m, color, z) is limited solely by the field of view of the
telescope and the exposure times adopted. Panchromatic data
matching that obtained with optical and near-infrared telescopes
from SIRTF, FIRST, and ALMA will also enable us unravel the cosmic
star formation history
SFR(z)
to unprecedented precision
([Madau et al 1996,
Blain et al 1999]).
It has already been claimed that
the above data, e.g. N(m, color, z) and
SFR(z),
can be
understood in terms of hierarchical models of structure formation
where galaxies assemble through the cooling of baryonic gas into
merging cold dark matter halos (CDM,
[Kauffmann
et al 1994,
Baugh et al 1998,
Cole et al 2000a]).
The word `concordance' was recently coined astrophysically in an article reconciling different estimates of the cosmological parameters ([Ostriker & Steinhardt 1996]). Such concordance in our understanding of galaxy evolution is a natural consequence of semi-analytical theories whose sole purpose is to explain the `big picture' as realised with the extant galaxy data. In this series of lectures I want to show that we have our work cut out for some considerable time! Exciting progress is definitely being made, but observers must rise to the challenge of testing the fundamentals of contemporary theories such as CDM and theorists must get ready to interpret qualitatively new kinds of data that we can expect in the next decade.
These lectures are intended for interested graduate students or postdocs entering the field. There is an obvious observational flavor although I have tried to keep in perspective an ultimate goal of comparing results with recent CDM predictions. The bias is largely to optical and near-infrared applications; there is insufficient space to do justice to the rapidly-developing contributions being made at sub-millimetre, radio and X-ray wavelengths which other contributors at this winter school will cover in detail.
2 A correlation was also made with three key international conferences ([Larson & Tinsley 1978, Frenk et al 1988, Livio, Fall & Madau 1998]) but I was horrified to see that these appeared to have had a negative effect on the community's output! I assume this arose from a much-needed period of post-conference reflection! Back.