Exploring Filament Galaxies Using AstroSat/UVIT

Abstract

We present results from our deep far-ultraviolet (FUV) survey using AstroSat/UVIT of a filamentary structure at z ∼0.072. A total of four filaments comprising 58 galaxies were probed in our study. We detect 18 filament galaxies in our FUV observation. All filament galaxies are further classified based on their photometric color, nuclear activity, and morphology. The filaments contain galaxies with mixed stellar population types and structures. We do not detect galaxies in our UVIT survey up to a distance of 0.4 Mpc h ^−1 from the filament axis, implying a lack of recent star formation in the inner region of filaments. The FUV star formation rate (SFR) for star-forming galaxies agrees well with the SFR _144MHz calculated using Low-Frequency Array radio-continuum observations. We witness an increase in the FUV specific-SFR (sSFR) of filament galaxies with increasing distance from the filament spine ( D _fil ). The intermediate-to-high stellar mass filament galaxies were more star-forming than cluster galaxies in a fixed stellar mass bin. The FUV morphology of some filament galaxies detected in the filament outskirts ( D _fil ≳ 0.7 Mpc h ^−1 ) is comparable to or slightly extended than their optical counterpart. The mass assembly of galaxies examined by estimating (FUV − r ) color gradients shows that more “red-cored’ galaxies reside in the outer region of the filaments. Our results prove that the likelihood of merger interaction and gas starvation increases when approaching the filament spine. We report a definitive and inhomogeneous impact of filaments on the galaxies residing inside them.

Keywords

• Ultraviolet astronomy
• Galaxy environments
• Large-scale structure of the universe
• Star formation
• Galaxy evolution