A High-Mass Size Deficit for Void Galaxies in the Complete SDSS DR7
Abstract
We characterize how environment shapes the sizes, luminosity functions, and mass functions of galaxies in large-scale underdensities by comparing the NSA catalog of the Sloan Digital Sky Survey Data Release 7 with an identically selected TNG300 sample, both built with the void finding algorithm VoidFinder, and by assigning a local average underdensity contrast to each galaxy via a spherical top-hat smoothed density field approximation. Void galaxies have fainter characteristic magnitudes than their non-void counterparts, and, at fixed stellar mass, redshift, and color, NSA void galaxies with M*>1011h−1M⊙ are about 11±3% more compact than galaxies in the field, a deficit the TNG300 simulation reproduces. The galaxies that are responsible for this effect are almost all central and predominantly early type, i.e., the systems that are most likely to grow their outer envelopes via late-time mergers. These trends hold across two redshift bins to z≤0.114. Crucially, this deficit is not a fixed property of the void sample but a steep function of the underdensity contrast, deepening toward the emptiest interiors and washing out at a typical density, implying that strict density control and sample selection are imperative when conducting environmental dependency studies like these. The same environmental dependence appears in the stellar mass function, which shifts to lower masses in the deepest voids, and in the close-pair (i.e., the ongoing merger) fraction, which falls toward the emptiest regions. Together, these point to a late-time, merger-driven growth of massive galaxies that is suppressed in voids, leaving their most massive members structurally distinct today.
Related
- The Size-Mass Relation and Inside-Out Quenching of Massive Quiescent Galaxies at 2<z<3 with JWST PRIMER and MINERVA
- HI rotation curves and mass-size relation for 568 galaxies from the Apertif Wide-area Extragalactic Survey
- Clustering-based halo mass assignment for high-redshift galaxies: method, validation, and application to JWST
- Mass-Dependent Dark Matter Deficit from Inelastic Scattering
- Origin of the Golden Mass of Galaxies and Black Holes
BibTeX
@misc{curtis2026highmass,
title = {{A High-Mass Size Deficit for Void Galaxies in the Complete SDSS DR7}},
author = {Olivia Curtis and Bryanne McDonough and Tereasa G. Brainerd},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.19253},
eprint = {2609.19253},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.19253},
}
RIS
TY - UNPB
TI - A High-Mass Size Deficit for Void Galaxies in the Complete SDSS DR7
AU - Olivia Curtis
AU - Bryanne McDonough
AU - Tereasa G. Brainerd
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.19253
UR - https://arxiv.org/abs/2609.19253
AB - We characterize how environment shapes the sizes, luminosity functions, and mass functions of galaxies in large-scale underdensities by comparing the NSA catalog of the Sloan Digital Sky Survey Data Release 7 with an identically selected TNG300 sample, both built with the void finding algorithm VoidFinder, and by assigning a local average underdensity contrast to each galaxy via a spherical top-hat smoothed density field approximation. Void galaxies have fainter characteristic magnitudes than their non-void counterparts, and, at fixed stellar mass, redshift, and color, NSA void galaxies with M_*>10^11h^−1M_⊙ are about 11±3% more compact than galaxies in the field, a deficit the TNG300 simulation reproduces. The galaxies that are responsible for this effect are almost all central and predominantly early type, i.e., the systems that are most likely to grow their outer envelopes via late-time mergers. These trends hold across two redshift bins to z≤0.114. Crucially, this deficit is not a fixed property of the void sample but a steep function of the underdensity contrast, deepening toward the emptiest interiors and washing out at a typical density, implying that strict density control and sample selection are imperative when conducting environmental dependency studies like these. The same environmental dependence appears in the stellar mass function, which shifts to lower masses in the deepest voids, and in the close-pair (i.e., the ongoing merger) fraction, which falls toward the emptiest regions. Together, these point to a late-time, merger-driven growth of massive galaxies that is suppressed in voids, leaving their most massive members structurally distinct today.
ER -