TheThreeHundred Project: ram pressure and gas content of haloes and subhaloes in the phase-space plane

Abstract

We use TheThreeHundred project, a suite of 324 resimulated massive galaxy clusters embedded in a broad range of environments, to investigate (i) how the gas content of surrounding haloes correlates with phase-space position at z = 0, and (ii) to investigate the role that ram pressure plays in this correlation. By stacking all 324 normalised phase-space planes containing 169287 haloes and subhaloes, we show that the halo gas content is tightly correlated with phase-space position. At ∼ 1.5−2 R 200 of the cluster dark matter halo, we find an extremely steep decline in the halo gas content of infalling haloes and subhaloes irrespective of cluster mass, possibly indicating the presence of an accretion shock. We also find that subhaloes are particularly gas-poor, even in the cluster outskirts, which could indicate active regions of ongoing pre-processing. By modelling the instantaneous ram pressure experienced by each halo and subhalo at z = 0, we show that the ram pressure intensity is also well correlated with phase-space position, which is again irrespective of cluster mass. In fact, we show that regions in the phase-space plane with high differential velocity between a halo or subhalo and its local gas environment, are almost mutually exclusive with high halo gas content regions. This suggests a causal link between the gas content of objects and the instantaneous ram pressure they experience, where the dominant factor is the differential velocity.

Gone after one orbit: How cluster environments quench galaxies

“…In contrast to the higher cluster mass intervals, the low mass range also exhibits a star-forming, albeit small, population with positive radial velocity, especially at high redshift, indicating that quenching becomes more effective at lower redshift and higher cluster mass. This is in agreement with a suite of recent cluster resimulations by Arthur et al (2019), which find ram-pressure stripping of subhalos to be significantly enhanced in more massive halos compared to less massive halos.…”

The Three Hundred project: the gas disruption of infalling objects in cluster environments

“…Their main finding showed that radial gas fractions decrease with decreasing cluster-centric distance, and contamination from backsplash and pre-processed galaxies (which will also increase with decreasing cluster-centric distance) brings the distribution down. This is in disagreement with Lotz et al (2019) and Arthur et al (2019), who find that the instantaneous gas fraction does decline radially, but the gas in (sub)haloes is lost on first passage, rather than contamination being the cause for the radial decline. In fact, in Arthur et al (2019), it was postulated that the majority of gas in infalling objects is stripped by some sort of accretion shock at 1.5-2R 200 , where R 200 is the radius of the halo at 200 times the critical density of the universe at that redshift.…”

“…This is in disagreement with Lotz et al (2019) and Arthur et al (2019), who find that the instantaneous gas fraction does decline radially, but the gas in (sub)haloes is lost on first passage, rather than contamination being the cause for the radial decline. In fact, in Arthur et al (2019), it was postulated that the majority of gas in infalling objects is stripped by some sort of accretion shock at 1.5-2R 200 , where R 200 is the radius of the halo at 200 times the critical density of the universe at that redshift. However, whilst galaxy star formation quenching has been well studied, a full examination of the gas in infalling objects is needed in order to possibly alleviate tension in the literature and learn more about pre-processing.…”

TheThreeHundred project: backsplash galaxies in simulations of clusters

“…Cosmological simulations show that ram pressure stripping is enhanced in cluster environments, and can lead to infalling galaxies being almost entirely stripped of their halo gas. This can occur even in the outskirts of a cluster, resulting in the quenching of star formation in cluster galaxies (Zinger et al 2018;Arthur et al 2019). Observational evidence for ram pressure stripping includes cluster galaxies whose molecular gas reservoirs have been disturbed, meaning the gas is distributed asymmetrically with respect to the stellar component of the galaxy (Zabel et al 2019).…”