Coherent Orientation Effects of Galaxies and Clusters

Abstract

Properties and distribution of galaxies on large scales appear to be an exercise in randomness. Our favorite quantifiers of these things, the correlation functions, are a little more than noise spectrum descriptors. It is thus not surprising that we are suspicious about any signs or reports of systematic coherence in that noisy world. Galaxy alignments in particular are prone to evoke skepticism. This is in the best spirit of a healthy scientific conservativism, but with a smattering of hypocrisy as well. The order out of chaos is really what we are hoping for, after all. To be more specific, any systematic behavior of “inborn” galaxian properties (that is, not acquired by subsequent evolution, e.g., by the ram-pressure stripping and its consequences) that depend on the large-scale environment would be a strong evidence in favor of the top-down formation scenarios; at most, galaxies and their parent large-scale structure could form at the same time, but the bottom-up scenarios would be in great difficulty to explain any such phenomena. Therein lies the deeper reason why most reports of large-scale coherence were greeted with doubts or controversy: due to a misfortunate historical accident, the theoretical cosmogony in english-speaking countries was stuck upon the hierarchical, bottom-up formation scenarios, and there is perhaps some inertia of belief, which mere data cannot shake too easily. To be fair, the burden of the proof is with the observers.