Galaxy Alignments in the Pisces-Perseus Supercluster Revisited

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Abstract
A search for preferential galaxy alignments in the Pisces-Perseus Supercluster (PPS) is made using the Minnesota Automated Plate Scanner Pisces-Perseus Survey (MAPS-PP). The MAPS-PP is a catalog of ~1400 galaxies with a (roughly) isophotal diameter greater than 30'' constructed from digitized scans of the blue and red plates of the Palomar Observatory Sky Survey covering the PPS. This is the largest sample of galaxies applied to a search of galaxy alignments in this supercluster, and it has been used in combination with previously published redshifts to construct the deepest PPS galaxy luminosity function to date. While previous studies have relied extensively on catalogs with visually estimated parameters for both sample selection and determination of galaxy orientation, the MAPS-PP uses selection criteria and measurements that are entirely machine and computer based. Therefore, it is not susceptible to some of the biases, such as the diameter inclination effect, known to exist in some other galaxy catalogs. The presence of anisotropic galaxy distributions is determined by use of the Kuiper statistic, a robust alternative to the χ2 statistic more traditionally used in these studies. Three statistically significant anisotropic distributions are observed. The reddest galaxies are observed to be oriented preferentially perpendicular to the local large-scale structure. The bluest galaxies near the supercluster plane are observed to have an anisotropic position angle distribution. Finally, a weak trend for the median position angle of color-selected galaxy subsamples to "twist" with increasing distance from the PPS plane is observed. These position angle distribution anisotropies are weak and are not consistent with any single primordial or modern-era galaxy alignment mechanism, although a mixture of such mechanisms is not ruled out.

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