Environmental Sculpting of Galaxy Structure at Fixed Stellar Mass: A Multi-Scale Analysis Across Cosmic Time using 3 Million HSC Galaxies

2026/05/18 by Caitlin Igel, Aritra Ghosh, Andrew J. Connolly +4 · 1 voice
Physics and Astronomy · #astro-ph.GA #astro-ph.CO

paper · pdf · doi:10.3847/1538-4357/ae771d

arxiv published 2026/05/18 · arxiv updated 2026/07/10

Abstract

The extent to which galaxy structure is shaped by environment beyond the local universe, once stellar mass is controlled, remains an open question in galaxy evolution. We address this challenge using an unprecedentedly large sample of ∼3 million galaxies from the Hyper Suprime-Cam Subaru Strategic Program spanning 0.3 ≤ z < 0.7 with log(M/M_\odot) ≥ 8.9. We correlate a mass-independent bulge-to-total ratio statistic with large-scale overdensity maps and cluster catalogs, propagating structural parameter posteriors through a Monte Carlo framework to robustly assess significance. We confirm with >5σ confidence that galaxy structure depends on environment at fixed stellar mass, but this dependence is secondary to stellar mass and varies with redshift, mass, and environmental scale. At z < 0.5, we detect no significant structural correlation with large-scale overdensity, but cluster galaxies show statistically significant bulge enhancement compared to mass-matched field galaxies, indicating cluster-specific processes such as ram-pressure stripping and cumulative tidal interactions dominate structural transformation at these epochs. At z ≥ 0.5, massive galaxies exhibit bulge-enhancement across both cluster- and large-scale environments, while lower-mass systems show enhancement only in cluster environments. This indicates that environmental mechanisms operate across broader spatial scales at earlier cosmic epochs, and enhanced merger rates, group preprocessing, and cosmic web stripping augment cluster-specific processes. By separating into star-forming and quiescent subsamples, we find nearly flat trends within each, demonstrating that the observed environmental effects arise from coupled morphological and star formation transformations. These results collectively reveal the multi-scale, epoch-dependent nature of environmental effects on galaxy structure.

Citations

• The SAGA Survey. VI. The Size-Mass Relation for Low-Mass Galaxies Across Environments
• AGN with massive black holes have closer galactic neighbors: k-Nearest-Neighbor statistics of an unbiased sample of AGN at z~0.03
• Effects of galactic environment on size and dark matter content in low-mass galaxies
• Denser Environments Cultivate Larger Galaxies: A Comprehensive Study beyond the Local Universe with 3 Million Hyper Suprime-Cam Galaxies
• How the Galaxy-Halo Connection Depends on Large-Scale Environment
• Array Programming with NumPy
• Galaxy Morphology Network: A Convolutional Neural Network Used to Study Morphology and Quenching in ∼ 100,000 SDSS and ∼ 20,000 CANDELS Galaxies
• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Second data release of the Hyper Suprime-Cam Subaru Strategic Program
• Pre-processing of galaxies in cosmic filaments around AMASCFI clusters in the CFHTLS
• Planck 2018 results: VI. Cosmological parameters
• The Connection between Galaxies and their Dark Matter Halos
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• First results on the cluster galaxy population from the Subaru Hyper Suprime-Cam survey. II. Faint end color-magnitude diagrams and radial profiles of red and blue galaxies at 0.1<z<1.1
• Effect of local environment and stellar mass on galaxy quenching and morphology at 0.5<z<2.0
• Photometric Redshifts for Hyper Suprime-Cam Subaru Strategic Program Data Release 1
• The Hyper Suprime-Cam SSP Survey: Overview and survey design
• Morphology and the Color-Mass Diagram as Clues to Galaxy Evolution at z~1
• An optically-selected cluster catalog at redshift 0.1<z<1.1 from the Hyper Suprime-Cam Subaru Strategic Program S16A data
• Cosmic Web of Galaxies in the COSMOS Field: Public Catalog and Different Quenching for Centrals and Satellites
• The role of mergers and halo spin in shaping galaxy morphology
• The COSMOS2015 Catalog: Exploring the 1<z<6 Universe with half a million galaxies
• Stellar mass functions: methods, systematics and results for the local Universe
• Strangulation as the primary mechanism for shutting down star formation in galaxies
• On the occurrence of galaxy harassment
• A cluster finding algorithm based on the multiband identification of red sequence galaxies
• The green valley is a red herring: Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early- and late-type galaxies★
• Astropy: A Community Python Package for Astronomy
• Galaxy evolution in groups and clusters: satellite star formation histories and quenching timescales in a hierarchical Universe
• Extragalactic Science, Cosmology and Galactic Archaeology with the Subaru Prime Focus Spectrograph (PFS)
• Galaxy evolution in groups and clusters: star formation rates, red sequence fractions, and the persistent bimodality
• Spitzer observations of Abell 1763 - II: Constraining the nature of activity in the cluster-feeding filament with VLA and XMM-Newton data
• The Merger Rates and Mass Assembly Histories of Dark Matter Haloes in the Two Millennium Simulations
• Physical Properties and Environments of Nearby Galaxies
• The accretion of galaxies into groups and clusters
• zCOSMOS – 10k-bright spectroscopic sample
• The role of environment in the morphological transformation of galaxies in 9 intermediate redshift clusters
• The zCOSMOS Redshift Survey: the role of environment and stellar mass in shaping the rise of the morphology-density relation from z~1
• The Effects of Gas on Morphological Transformation in Mergers: Implications for Bulge and Disk Demographics
• The Structures of Distant Galaxies - III: The Merger History of over 20,000 Massive Galaxies at z < 1.2
• Post-starburst galaxies: more than just an interesting curiosity
• Galaxy Zoo: the dependence of morphology and colour on environment
• LSST: from Science Drivers to Reference Design and Anticipated Data Products
• The Dependence of Galaxy Morphology and Structure on Environment and Stellar Mass
• The Evolution of the Field and Cluster Morphology-Density Relation for Mass-Selected Samples of Galaxies
• A Cosmological Framework for the Co-Evolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies: II. Formation of Red Ellipticals
• Galaxy bimodality versus stellar mass and environment
• The Morphology - Density Relation in z ~ 1 Clusters
• The Environmental Dependence of the Relations between Stellar Mass, Structure, Star Formation and Nuclear Activity in Galaxies
• Pre-Processing of Galaxies before Entering a Cluster
• Relationship between environment and the broad-band optical properties of galaxies in the SDSS
• Quantifying the Bimodal Color‐Magnitude Distribution of Galaxies
• Color Separation of Galaxy Types in the Sloan Digital Sky Survey Imaging Data
• Hierarchical Evolution in Poor Groups of Galaxies
• Evolution since z = 0.5 of the Morphology-Density relation for Clusters of Galaxies
• Galaxy Harassment and the Evolution of Clusters of Galaxies
• Hyper Suprime-Cam: System design and verification of image quality

Discussions

• For more details, head to arxiv.org/abs/2605.18963 Co-led this with my student Caitlin Igel. Also shoutouts to our other co-authors: Andy Connolly, Brant Robertson, Meg Urry, Louise Edwards & Rhythm S [bsky, 0 points, 0 comments]

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