Impact of Cosmic Filaments on the Gas Accretion Rate of Dark Matter Halos

Abstract

We investigate the impact of cosmic filaments on the gas accretion rate, ${\dot{M}}_{\mathrm{gas}}$ , of dark matter halos in filaments, based on cosmological hydrodynamic simulation. We find that for halos less massive than 10^12.0 M _⊙, ${\dot{M}}_{\mathrm{gas}}$ of halos residing in prominent filaments (with width D _fil > 3 Mpc h ⁻¹) is lower than halos residing in tenuous filaments (D _fil < 3 Mpc h ⁻¹) by 20%–30% at z = 0.5 and by a factor of 2–3 at z = 0. However, ${\dot{M}}_{\mathrm{gas}}$ depends weakly on the physical distance between halo center and the spine of filaments from high redshift to z = 0 and only shows a clear difference between the inner and outer regions in prominent filaments at z = 0. We further probe the thermal properties of gas in prominent and tenuous filaments, which appear in relatively highly and intermediate overdense regions, respectively. The gas in prominent filaments is hotter. Around 26%, 38%, and 45% of gases in prominent filaments are hotter than 10⁶ K at z = 1.0, 0.5, and 0.0, respectively. The corresponding fractions in tenuous filaments are merely ∼6%, 9%, and 11%. The suppressed gas accretion rate for low-mass halos in prominent filaments at z ≲ 0.5 may result from the hotter ambient gas, which could provide a physical processing mechanism to cut down the supply of gas to halos before they enter clusters. This process partially meets the need of the preheating mechanism implemented in some semianalytical models of galaxy formation but works only for ∼20% of halos at z < 1.