Galaxy transformation across the cosmic web: Evolution of stellar colours and star formation rates in filaments

¹ Instituto de Astrofísica de Canarias, calle Vía Láctea s/n, E-38205 La Laguna, Tenerife, Spain
² Departamento de Astrofísica, Universidad de La Laguna, Avenida Astrofísico Francisco Sánchez s/n, E-38206 La Laguna, Spain
³ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Unidad Asociada al CSIC, Plaza San Juan 1, 44001 Teruel, Spain

^⋆ Corresponding author: szarattini@cefca.es

Received: 18 November 2024
Accepted: 31 March 2025

Abstract

Context. The aim of this work is to provide evidence of the imprints left by large-scale structure on galaxy properties by selecting extensive samples of galaxies from different environments, while matching their intrinsic and local environmental characteristics.

Aims. We investigated the effects of the large-scale structure on the g − r stellar colour and star formation rate (SFR) in galaxies with stellar mass M_* > 10¹⁰ M_⊙, within the redshift range 0.05 ≤ z ≤ 0.1, and selected from the main galaxy sample of the Sloan Digital Sky Survey Data Release 16. We used a spectroscopic catalogue available in the literature to define samples of galaxies located in field and filament environments.

Methods. Galaxies located in the field tend to exhibit bluer g − r stellar colours and higher SFR than those in filaments. These differences persist even in samples of galaxies matched by mass and galaxy local overdensity, indicating that they are not produced by internal or local environmental processes. These differences cannot be attributed to variations in morphology between the two matched samples. There is also a variation in stellar colour and SFR with distance to the filaments (D_fila). The SFR of galaxies becomes statistically smaller than that of field galaxies for objects located at D_fila < 5 Mpc, while changes in stellar colour occur at smaller distances (D_fila < 1 Mpc). This could indicate that the typical filament width is about 2.5–5 Mpc.

Results. The variations in colour and SFR between galaxy samples in the field and in filaments, with matched masses and local overdensities, indicate that large-scale environmental factors drive these transformations rather than local or internal galaxy properties. These transformations are not strong enough to produce changes in galaxy morphology. They could be explained by a cosmic web starvation process, in which galaxies moving from the field into filaments become detached from their gas supply, leading to a gradual decline in SFR and a subsequent reddening of their stellar populations.