Statistically significant length scale of filaments as a robust measure of galaxy distribution

TL;DR

This study demonstrates that the statistically significant length scale of filaments in galaxy distributions is a robust, property-independent measure that aligns with Lambda CDM model predictions and is minimally affected by bias or sample density.

Contribution

We establish the robustness of the filament length scale as a measure of galaxy distribution, independent of galaxy properties, bias, and sample density, validated through SDSS data and simulations.

Findings

The filament length scale does not depend on galaxy luminosity, colour, or morphology.

Lambda CDM simulations agree with observed filament length scales.

The method reliably recovers filament lengths in controlled tests.

Abstract

We have used a statistical technique "Shuffle" (Bhavsar & Ling 1988; Bharadwaj, Bhavsar & Sheth 2004) in seven nearly two dimensional strips from the Sloan Digital Sky Survey Data Release Six (SDSS DR6) to test if the statistically significant length scale of filaments depends on luminosity, colour and morphology of galaxies. We find that although the average filamentarity depends on these galaxy properties, the statistically significant length scale of filaments does not depend on them. We compare it's measured values in SDSS against the predictions of Lambda CDM N-body simulations and find that Lambda CDM model is consistent with observations. The average filamentarity is known to be very sensitive to the bias parameter. Using Lambda CDM N-body simulations we simulate mock galaxy distributions for SDSS NGP equatorial strip for different biases and test if the statistically significant length scale of filaments depends on bias. We find that statistically significant length scale of filaments is nearly independent of bias. The average filamentarity is also known to be dependent on the galaxy number density and size of the samples. We use Lambda CDM dark matter N-body simulations to test if the statistically significant length scale of filaments depends on these factors and find a very weak dependence. Finally we test the reliability of our method by applying it to controlled samples of segment Cox process and find that our method successfully recovers the length of the inputted segments. Summarizing these results we conclude that the statistically significant length scale of filaments is a robust measure of the galaxy distribution.