The Sloan Digital Sky Survey: Past and Future
The field of cosmology has evolved from an exceedingly data-starved field driven almost entirely by theoretical ideas barely a decade ago to one today in which there exist vast, rich sets of still relatively undigested data which are being used to confront theoretical models in great detail. For the first time in the history of the subject the data are good enough to constrain the cosmological model with some precision. After decades of apparent inconsistencies based on the analyses of small, poorly understood data sets, essentially all of the good current data from a vast variety of sources suggest that the universe is adequately described by a single ``concordance" model of an entirely different nature than envisaged by cosmologists barely a decade ago: one in which the energetics of the expansion are currently dominated by a cosmological-constant-like `dark energy', much more important at the present epoch than the dark matter which has been known for a long time to dominate the rest mass density. The nature of this component has joined the nature of the dark matter as the most pressing and difficult questions facing cosmology today.
The data from which these conclusions have been reached come from many sources, but the chief contributors have been studies of the cosmic microwave background, optical studies of distant type 1a supernovae, and large optical redshift surveys, most notably the Anglo-Australian 2dF survey and the Sloan Digital Sky Survey (SDSS) with which the author has been associated for many years.
Statistical studies of the large scale structure in the distribution of galaxies was one of the prime reasons the SDSS was initiated, and the results have more than satisfied our expectations. Additional and supporting data have come from unanticipated directions in the survey, including studies of the Lyman-alpha forest spectra in quasars and from statistical studies of weak gravitational lensing. The survey data have by no means been exhaustively analyzed; indeed, most of the conclusions reached so far have come from relatively small subsets of the survey data, which will not be all in hand for approximately two years. I will discuss the results and precision we have obtained and those we expect from the full survey.
In a three-year extension of the original survey, currently funded and underway, we are undertaking also a new galactic structure survey and a moderate-redshift supernova survey, and I will discuss these. Finally, I will preview briefly the expected capabilities of planned next-generation optical surveys.
