Spectroscopic Study of Star-forming Galaxies in Filaments and the Field at $z\sim$0.5: Evidence for Environmental Dependence of Electron Density

TL;DR

This study compares the physical properties of star-forming galaxies in a large filament at z~0.53 with those in the field, revealing environmental effects on metallicity and electron density that influence galaxy evolution.

Contribution

It provides the first spectroscopic evidence of environmental dependence of electron density and metallicity in filamentary structures at intermediate redshift.

Findings

Filament galaxies are more metal-enriched than field galaxies.

Electron densities are significantly lower in filament galaxies.

Similar ionization parameters and star-formation indicators in both environments.

Abstract

We study the physical properties of a spectroscopic sample of 28 star-forming galaxies in a large filamentary structure in the COSMOS field at $z\sim$0.53, with spectroscopic data taken with the Keck/DEIMOS spectrograph, and compare them with a control sample of 30 field galaxies. We spectroscopically confirm the presence of a large galaxy filament ($\sim$ 8 Mpc), along which five confirmed X-ray groups exist. We show that within the uncertainties, the ionization parameter, equivalent width (EW), EW versus specific star-formation rate (sSFR) relation, EW versus stellar mass relation, line-of-sight velocity dispersion, dynamical mass, and stellar-to-dynamical mass ratio are similar for filament and field star-forming galaxies. However, we show that on average, filament star-forming galaxies are more metal-enriched ($\sim$ 0.1$-$0.15 dex), possibly due to the inflow of the already enriched intrafilamentary gas into filament galaxies. Moreover, we show that electron densities are significantly lower (a factor of $\sim$17) in filament star-forming systems compared to those in the field, possibly because of a longer star-formation timescale for filament star-forming galaxies. Our results highlight the potential pre-processing role of galaxy filaments and intermediate-density environments on the evolution of galaxies, which has been highly underestimated.