The Large Scale Structure of the Universe

Abstract

The study of large scale structure is one of the most dynamically evolving areas of astrophysics today. Cosmology and large scale structure is growing into an accurate science and requires correspondingly more sophisticated methods of analysis. Twenty years ago the estimates of the fluctuation amplitude were about 10^-3, almost a factor of 100 off of today’s measurements. Ten years ago we could only hope for high precision measurements of large scale structure, there were less than 5000 redshifts measured, and only a handful of normal galaxies with z > 1 were known. Computer models of structure formation had just begun to consider non-power-law spectra based on physical models like hot/cold dark matter. As a consequence there was considerable freedom in adjusting parameters in the various galaxy formation scenarios. In contrast, many of today’s debates are about factors of 2 and soon we will be arguing about 10% differences. The shape of the primordial fluctuation spectrum, first derived from philosophical arguments [2, 1], can now be quantified from detections of fluctuations in the CBR made by COBE[3]. The number of available redshifts is beyond 50,000, and soon we will have redshift surveys surpassing 1 million galaxies. N-body simulations are becoming more sophisticated, of higher resolution, and incorporating complex gas dynamics. The unprecedented number of new observations currently under way give us hope that over the next decade we will gain a clear understanding of the shape and evolution of the primordial fluctuation spectrum, understand from first principles how galaxies were formed, and make quantitative comparisons and tests to differentiate among the various galaxy formation scenarios.