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Voids in SDSS DR7: Updated catalogs and their impact on galaxy classification

Presentation #139.23 in the session Galaxy Clusters/Large Scale Structure, Cosmic Distance — iPoster Session.

Published onJun 29, 2022
Voids in SDSS DR7: Updated catalogs and their impact on galaxy classification

We investigate how the definition of a void affects our understanding of galaxy formation and evolution by comparing two different void-finding algorithms. First, we produce several public void catalogs using a volume-limited subsample of the Sloan Digital Sky Survey Data Release 7 (SDSS DR7). We then explore how the definition of a void influences the conclusions drawn about the impact of the void environment on galaxy properties. Using new implementations of two different void-finding algorithms in the Void Analysis Software Toolkit (VAST), VoidFinder and V2 (a ZOBOV-based algorithm), we identify 1159 and 531 cosmic voids with radii > 10 Mpc/h, respectively, out to a redshift of z = 0.114. We compute effective radii and centers for all voids and find none with an effective radius > 54 Mpc/h; the median void effective radius is 15-17 Mpc/h in each void catalog. We find that galaxies found in VoidFinder voids tend to be bluer, fainter, and have higher (specific) star formation rates than galaxies in denser regions. Conversely, galaxies found in V2 voids show no significant differences when compared to galaxies in denser regions, which is inconsistent with large-scale environmental effects on galaxy properties expected from both simulations and previous observations. We propose that V2-identified voids “leak” into the dense walls between voids because their boundaries extend up to the density maxima within the walls. As a result, when using ZOBOV-based void finders, galaxies likely to be part of wall regions are instead classified as void galaxies. This misclassification of galaxies can affect our understanding of galaxy evolution.

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