The size of the longest filament in the Luminous Red Galaxy distribution

TL;DR

This study analyzes the filamentary structure of Luminous Red Galaxies in SDSS DR7, finding that the largest statistically significant filaments are about 110 Mpc/h long, with longer structures likely due to chance.

Contribution

It introduces a statistical method to determine the maximum significant filament length in galaxy distributions, applied to SDSS data.

Findings

Maximum significant filament length is about 110 Mpc/h.

Filamentarity exceeds that of random distributions.

Longer filaments are statistically insignificant.

Abstract

Filaments are one of the most prominent features visible in the galaxy distribution. Considering the Luminous Red Galaxies (LRGs) in the Sloan Digital Sky Survey Data Release Seven (SDSS DR7), we have analyzed the filamentarity in 11 nearly two dimensional (2D) sections through a volume limited subsample of this data. The galaxy distribution, we find, has excess filamentarity in comparison to a random distribution of points. We use a statistical technique "Shuffle" to determine $L_{\rm MAX}$, the largest length-scale at which we have statistically significant filaments. We find that $L_{\rm MAX}$ varies in the range $100-130 \, h^{-1} {\rm Mpc}$ across the 11 slices, with a mean value $L_{\rm MAX}=110 \pm 12 \, h^{-1}{\rm Mpc}$. Longer filaments, though possibly present in our data, are not statistically significant and are the outcome of chance alignments.