Galaxies in voids assemble their stars slowly

TL;DR

This study demonstrates that galaxies in cosmic voids have slower star formation histories compared to those in denser environments, with two main SFH types affected differently by their surroundings.

Contribution

It provides the first observational evidence that void galaxies form stars more slowly than their counterparts in denser regions, highlighting environment's role in galaxy evolution.

Findings

Void galaxies have slower SFHs than those in denser environments.

Two main SFH types are identified: short-timescale and long-timescale.

Both SFH types evolve more slowly in voids.

Abstract

Galaxies in the Universe are distributed in a web-like structure characterised by different large-scale environments: dense clusters, elongated filaments, sheetlike walls, and under-dense regions, called voids. The low density in voids is expected to affect the properties of their galaxies. Indeed, previous studies have shown that galaxies in voids are on average bluer and less massive, and have later morphologies and higher current star formation rates than galaxies in denser large-scale environments. However, it has never been observationally proved that the star formation histories (SFHs) in void galaxies are substantially different from those in filaments, walls, and clusters. Here we show that void galaxies have had, on average, slower SFHs than galaxies in denser large-scale environments. We also find two main SFH types present in all the environments: 'short-timescale' galaxies are not affected by their large-scale environment at early times but only later in their lives; 'long-timescale' galaxies have been continuously affected by their environment and stellar mass. Both types have evolved slower in voids than in filaments, walls, and clusters.