CHILES. IX. Observational and Simulated H i Content and Star Formation of Blue Galaxies in Different Cosmic Web Environments

Abstract

We examine the redshift evolution of the relationship between the neutral atomic hydrogen (H I) content and star formation properties of blue galaxies, along with their location in the cosmic web. Using the COSMOS H I Large Extragalactic Survey (CHILES) and the IllustrisTNG (TNG100) cosmological simulation, and the DISPERSE algorithm, we identify the filamentary structure in both observations and simulations, measure the distance of galaxies to the nearest filament spine Dfil , and calculate the mean H I gas fraction and the relative specific star formation rate (sSFR) of blue galaxies in three different cosmic web environments—0 < Dfil/Mpc < 2 (filament cores), 2 < Dfil/Mpc < 4 (filament outskirts), and 4 < Dfil/Mpc < 20 (voids). We find that, although there are some similarities between CHILES and TNG, there exist significant discrepancies in the dependence of H I and star formation on the cosmic web and on redshift. TNG overpredicts the observed H I fraction and relative sSFR at z = 0–0.5, with the tension being strongest in the voids. CHILES observes a decline in the H I fraction from filament cores to voids, exactly the opposite of the trend predicted by TNG. CHILES observes an increase in H I fraction at z = 0.5 → 0 in the voids, while TNG predicts an increase in this time in all environments. Further dividing the sample into stellar mass bins, we find that the H I in / ( )M Mlog 10>* galaxies is better reproduced by TNG than H I in / ( )M Mlog 9 10= -* galaxies.