Filament and shape statistics: A quantitative comparison of cold + hot and cold dark matter cosmologies versus CfA1 data

A new class of geometric statistics for analysing galaxy catalogues is presented. Filament statistics quantify filamentarity and planarity in large-scale structure in a manner consistent with catalogue visualizations. These statistics are based on sequences of spatial links which follow local high-density structures. From these link sequences we compute the discrete curvature, planarity, and torsion. Filament statistics are applied to cold dark matter (CDM) and cold + hot dark matter (CHDM) (Ω=0.3) simulations of Klypin et al., the CfA1-like mock redshift catalogues of Nolthenius, Klypin & Primack, and the CfA1 catalogue. We also apply the moment-based shape statistics developed by Babul & Starkman, Luo & Vishniac and Robinson & Albrecht to these same catalogues, and compare their robustness and discriminatory power versus filament statistics. For 100-Mpc periodic simulation boxes (H₀=50 km s^-1 Mpc^-1), we find discrimination of ∼4σ (where σ represents resampling errors) between CHDM and CDM for selected filament statistics and shape statistics, including variations in the galaxy identification scheme. Comparing the CfA1 data versus the models does not yield a conclusively favoured model; no model is excluded at more than a ∼ 2σ level for any statistic, not including cosmic variance which could further degrade the discriminatory power. We find that CfA1 discriminates poorly between models, mainly because of its sparseness and small number of galaxies, not as a result of redshift distortion, magnitude limiting or geometrical effects. We anticipate that the proliferation of large redshift surveys and simulations will enable the statistics presented here to provide robust discrimination between large-scale structure in various cosmological models.