NeutralUniverseMachine: How Filaments and Dark Matter Halo Influence the Galaxy Cold Gas Content

Abstract

Aims. To investigate the influence of distance to filaments and dark matter halos on galaxy cold gas content in the empirical model NeutralUniverseMachine (NUM) and the hydrodynamical simulation IllustrisTNG. Methods. We use DisPerSE to identify cosmic web structures and calculate the distance of galaxies to filaments for both observations and models. We show the results of the HI and H2 mass functions, HI- and H2-halo mass relations, HI- and H2-stellar mass relations for galaxies in the NUM model and IllustrisTNG with different distances to filaments and compare them with observational measurements. We also show the evolution of HI, H2 mass densities in different distance to filament bins. Results. We find that the role of filaments in affecting the HI gas is generally less significant compared to the halo environment. There is a weak trend in the observations at z = 0 that low-mass halos lying closer to filaments tend to have reduced HI masses. However, this trend reverses for massive halos with log(Mvir/Msun) > 12.5. This behavior is accurately reproduced in the NUM model due to the dependence of HI gas on the halo formation time, but it does not appear in IllustrisTNG. The influence of filaments on the HI gas becomes slightly weaker at higher redshifts and is only significant for galaxies residing in massive halos in the NUM model. Filaments have almost no impact on the H2-stellar mass relation in both models, confirming that H2 is primarily determined by the galaxy stellar mass and star formation rate.