Impact of cosmic filaments on the gas accretion rate of dark matter halos

TL;DR

This study uses cosmological hydrodynamic simulations to show that cosmic filament properties significantly influence gas accretion rates and thermal states of dark matter halos, especially for low-mass halos at low redshift.

Contribution

It reveals how filament density and temperature affect gas accretion onto halos, highlighting a physical mechanism for preheating that impacts galaxy formation models.

Findings

Lower gas accretion in prominent filaments for halos <10^12 M_sun at z=0.5 and z=0.

Hotter gas in prominent filaments correlates with suppressed accretion.

Hot gas fractions increase over time, especially in prominent filaments.

Abstract

We investigate the impact of cosmic filaments on the gas accretion rate, $\dot{M}_{\rm{gas}}$, of dark matter halos in filaments, based on cosmological hydrodynamic simulation. We find that for halos less massive than $10^{12.0}\ \rm{M_{\odot}}$, $\dot{M}_{\rm{gas}}$ of halos residing in prominent filaments (with width $D_{\rm{fil}}>3\ \rm{Mpc}/h$) is lower than halos residing in tenuous filaments ($D_{\rm{fil}}<3\ \rm{Mpc}/h$) by $20-30\%$ at $z=0.5$, and by a factor of 2-3 at $z=0$. However, $\dot{M}_{\rm{gas}}$ depends weakly on the physical distance between halo center and the spine of filaments from high redshift to $z=0$, only shows 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 $10^6$ K at $z=1.0, 0.5$ and $z=0.0$ respectively. The corresponding fractions in tenuous filaments are merely $\sim 6\%, 9\%$ and $11\%$. The suppressed gas accretion rate for low-mass halos in prominent filaments at $z \lesssim 0.5$ 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 meets partially the need of the preheating mechanism implemented in some semi-analytical models of galaxy formation, but works only for $\sim 20\%$ of halos at $z < 1$.