5.3. Some Possible Cosmogenic Scenarios

5.3.1. The Power Spectrum of the Galaxy Distribution

One of the strongest observational constraints on structure formation scenarios is provided by the observed power spectrum of the galaxy distribution. This is shown in Figure 5-1 in which power is plotted as a function of scale. Note that this is plotted in log-log space. Although different redshift surveys (e.g., Schuecker et al. 1996; Lin et al. 1996; Mo and Fukugita 1996; Klypin et al. 1996; Oliver et al. 1996;) produce slightly different variants of this diagram. As such, Figure 5-1 is a good characterization and shows the general tendency for stronger clustering on smaller scales. The point at the largest scale ( 200 h^-1 Mpc) is the most uncertain. Some redshift surveys indicate a turnover in power on this scale, while others have it uniformly rising. The important point, however, is that large scale power does exist and needs to be accounted for by the model. The three models (from Park et al. 1994) which are fit to the power spectrum in Figure 5-1 are:

Figure 5-1: Power spectrum from Park et al. (1994). The bottom solid line is standard CDM normalized to the small scale. The upper solid line is standard CDM normalized to the larger scale. The dashed line is an open universe or LAMBDA dominated model.

The dashed line in Figure 5-1 is the model which fits the data best. This model can be the either an open Universe model, which is not directly allowed for by the inflationary paradigm, or a spatially flat model which has a non-zero Cosmological Constant.