The role of baryon models in hydrodynamic simulations is still unclear. Future surveys that use cluster statistics to precisely constrain cosmological models require a better understanding of the ...baryonic effects. Using the hydro-simulated galaxy clusters from different baryon models (Gadget-MUSIC, Gadget-X and Gizmo-SIMBA) from the THREEHUNDRED project, we can address this question into more details. We find that the galaxy cluster mass change due to different baryon models is at a few per cent level. However, the mass changes can be positive or negative depending on the baryon models. Such a small mass change leaves a weak influence (slightly larger compared to the mass changes) on both the cumulative halo numbers and the differential halo mass function (HMF) above the mass completeness. Similarly to to the halo mass change, the halo mass or the HMF can be increased or decreased with respect to the dark-matter-only (DMO) run depending on the baryon models.
We investigate baryon effects on the halo mass function (HMF), with emphasis on the role played by active galactic nuclei (AGN) feedback. Haloes are identified with both friends-of-friends (FoF) and ...spherical overdensity (SO) algorithms. We embed the standard SO algorithm into a memory-controlled frame program and present the Python spherIcAl Overdensity code – piao (Chinese character: ). For both FoF and SO haloes, the effect of AGN feedback is that of suppressing the HMFs to a level even below that of dark matter (DM) simulations. The ratio between the HMFs in the AGN and in the DM simulations is ∼0.8 at overdensity Δc = 500, a difference that increases at higher overdensity Δc = 2500, with no significant redshift and mass dependence. A decrease of the halo masses ratio with respect to the DM case induces the decrease of the HMF in the AGN simulation. The shallower inner density profiles of haloes in the AGN simulation witnesses that mass reduction is induced by the sudden displacement of gas induced by thermal AGN feedback. We provide fitting functions to describe halo mass variations at different overdensities, which can recover the HMFs with a residual random scatter ≲5 per cent for halo masses larger than 1013 h
−1 M⊙.
Abstract The main systematics in cluster cosmology is the uncertainty in the mass–observable relation. In this paper, we focus on the most direct cluster observable in optical surveys, i.e., ...richness, and constrain the intrinsic mass–richness (MR) relation of clusters in THE THREE HUNDRED hydrodynamic simulations with two runs: GIZMO-SIMBA and GADGET-X. We find that modeling the richness at a fixed halo mass with a skewed Gaussian distribution yields a simpler and smaller scatter compared to the commonly used lognormal distribution. Additionally, we observe that baryon models have a significant impact on the scatter while exhibiting no influence on the mass dependence and a slight effect on the amplitude in the MR relation. We select member galaxies based on both stellar mass M ⋆ and absolute magnitude M . We demonstrate that the MR relations obtained from these two selections can be converted to each other by using the M ⋆ – M relation. Finally, we provide a seven-parameter fitting result comprehensively capturing the dependence of the MR relation on both stellar mass cutoff and redshift.
The effects of baryons on the halo mass function Cui, Weiguang; Borgani, Stefano; Dolag, Klaus ...
Monthly Notices of the Royal Astronomical Society,
July 2012, Letnik:
423, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We present an analysis of the effects of baryon physics on the halo mass function. The analysis is based on simulations of a cosmological volume having a comoving size of 410 h
−1 Mpc, which have ...been carried out with the tree-pm/smoothed particle hydrodynamics code gadget-3, for a Wilkinson Microwave Anisotropy Probe-7 Λ cold dark matter cosmological model. Besides a dark matter (DM)-only simulation, we also carry out two hydrodynamical simulations: the first one includes non-radiative physics, with gas heated only by gravitational processes; the second one includes radiative cooling, star formation and kinetic feedback in the form of galactic ejecta triggered by supernova explosions. All simulations follow the evolution of two populations of 10243 particles each, with mass ratio such that to reproduce the assumed baryon density parameter, with the population of lighter particles assumed to be collisional in the hydrodynamical runs. We identified haloes using a spherical overdensity algorithm and their masses are computed at three different overdensities (with respect to the critical one), Δc= 200, 500 and 1500.
We find the fractional difference between halo masses in the hydrodynamical and in the DM simulations to be almost constant, at least for haloes more massive than
. In this range, mass increase in the hydrodynamical simulations is of about 4-5 per cent at Δc= 500 and ∼1-2 per cent at Δc= 200. Quite interestingly, these differences are nearly the same for both radiative and non-radiative simulations. Mass variations depend on halo mass and physics included for higher overdensity, Δc= 1500, and smaller masses. Such variations of halo masses induce corresponding variations of the halo mass function (HMF). At z= 0, the HMFs for gravitational heating and cooling and star formation simulations are close to the DM one, with differences of ≲3 per cent at Δc= 200, and ≃7 per cent at Δc= 500, with ∼10-20 per cent differences reached at Δc= 1500. At this higher overdensity, the increase of the HMF for the radiative case is larger by about a factor of 2 with respect to the non-radiative case. Assuming a constant mass shift to rescale the HMF from the hydrodynamic to the DM simulations, brings the HMF difference with respect to the DM case to be consistent with zero, with a scatter of ≲3 per cent at Δc= 500 and ≲2 per cent at Δc= 200.
Our results have interesting implications for assessing uncertainties in the mass function calibration associated with the uncertain baryon physics, in view of cosmological applications of future large surveys of galaxy clusters.
ABSTRACT
Galaxy clusters grow by accreting galaxies from the field and along filaments of the cosmic web. As galaxies are accreted they are affected by their local environment before they enter ...(pre-processing), and traverse the cluster potential. Observations that aim to constrain pre-processing are challenging to interpret because filaments comprise a heterogeneous range of environments including groups of galaxies embedded within them and backsplash galaxies that contain a record of their previous passage through the cluster. This motivates using modern cosmological simulations to dissect the population of galaxies found in filaments that are feeding clusters, to better understand their history, and aid the interpretation of observations. We use zoom-in simulations from The ThreeHundred project to track haloes through time and identify their environment. We establish a benchmark for galaxies in cluster infall regions that supports the reconstruction of the different modes of pre-processing. We find that up to 45 per cent of all galaxies fall into clusters via filaments (closer than 1 h−1Mpc from the filament spine). 12 per cent of these filament galaxies are long-established members of groups and between 30 and 60 per cent of filament galaxies at R200 are backsplash galaxies. This number depends on the cluster’s dynamical state and sharply drops with distance. Backsplash galaxies return to clusters after deflecting widely from their entry trajectory, especially in relaxed clusters. They do not have a preferential location with respect to filaments and cannot collapse to form filaments. The remaining pristine galaxies (∼30–60 per cent) are environmentally affected by cosmic filaments alone.
ABSTRACT
Galaxy cluster outskirts are described by complex velocity fields induced by diffuse material collapsing towards filaments, gas, and galaxies falling into clusters, and gas shock processes ...triggered by substructures. A simple scenario that describes the large-scale tidal fields of the cosmic web is not able to fully account for this variety, nor for the differences between gas and collisionless dark matter. We have studied the filamentary structure in zoom-in resimulations centred on 324 clusters from the threehundred project, focusing on differences between dark and baryonic matter. This paper describes the properties of filaments around clusters out to five R200, based on the diffuse filament medium where haloes had been removed. For this, we stack the remaining particles of all simulated volumes to calculate the average profiles of dark matter and gas filaments. We find that filaments increase their thickness closer to nodes and detect signatures of gas turbulence at a distance of ${\sim}2 \rm {{{~h^{-1}\,{\rm Mpc}}}$ from the cluster. These are absent in dark matter. Both gas and dark matter collapse towards filament spines at a rate of ${\sim}200 \,\rm {km ~ s^{-1}\, h^{-1}}$. We see that gas preferentially enters the cluster as part of filaments, and leaves the cluster centre outside filaments. We further see evidence for an accretion shock just outside the cluster. For dark matter, this preference is less obvious. We argue that this difference is related to the turbulent environment. This indicates that filaments act as highways to fuel the inner regions of clusters with gas and galaxies.
Intracluster light (ICL) in observations is usually identified through the surface brightness limit (SBL) method. In this paper, for the first time we produce mock images of galaxy groups and ...clusters, using a cosmological hydrodynamical simulation to investigate the ICL fraction and focus on its dependence on observational parameters, e.g., the SBL, the effects of cosmological redshift-dimming, point-spread function (PSF), and CCD pixel size. Detailed analyses suggest that the width of the PSF has a significant effect on the measured ICL fraction, while the relatively small pixel size shows almost no influence. It is found that the measured ICL fraction depends strongly on the SBL. At a fixed SBL and redshift, the measured ICL fraction decreases with increasing halo mass, while with a much fainter SBL, it does not depend on halo mass at low redshifts. In our work, the measured ICL fraction shows a clear dependence on the cosmological redshift-dimming effect. It is found that there is more mass locked in the ICL component than light, suggesting that the use of a constant mass-to-light ratio at high surface brightness levels will lead to an underestimate of ICL mass. Furthermore, it is found that the radial profile of ICL shows a characteristic radius that is almost independent of halo mass. The current measurement of ICL from observations has a large dispersion due to different methods, and we emphasize the importance of using the same definition when observational results are compared with theoretical predictions.
We analyse the basic properties of brightest cluster galaxies (BCGs) produced by state of the art cosmological zoom-in hydrodynamical simulations. These simulations have been run with different ...subgrid physics included. Here we focus on the results obtained with and without the inclusion of the prescriptions for supermassive black hole growth and of the ensuing active galactic nuclei (AGN) feedback. The latter process goes in the right direction of decreasing significantly the overall formation of stars. However, BCGs end up still containing too much stellar mass, a problem that increases with halo mass, and having an unsatisfactory structure. This is in the sense that their effective radii are too large, and that their density profiles feature a flattening on scales much larger than observed. We also find that our model of thermal AGN feedback has very little effect on the stellar velocity dispersions, which turn out to be very large. Taken together, these problems, which to some extent can be recognized also in other numerical studies typically dealing with smaller halo masses, indicate that on one hand present day subresolution models of AGN feedback are not effective enough in diminishing the global formation of stars in the most massive galaxies, but on the other hand they are relatively too effective in their centres. It is likely that a form of feedback generating large-scale gas outflows from BCGs precursors, and a more widespread effect over the galaxy volume, can alleviate these difficulties.
ABSTRACT
Concentration is one of the key dark matter halo properties that could drive the scatter in the stellar-to-halo mass relation of massive clusters. We derive robust photometric stellar masses ...for a sample of brightest central galaxies (BCGs) in SDSS redmapper clusters at 0.17 < z < 0.3, and split the clusters into two equal-halo mass subsamples by their BCG stellar mass $M_*^{\mathrm{BCG}}$. The weak lensing profiles ΔΣ of the two cluster subsamples exhibit different slopes on scales below $1\, h^{-1}\, {\mathrm{Mpc}}$. To interpret such discrepancy, we perform a comprehensive Bayesian modelling of the two ΔΣ profiles by including different levels of miscentring effects between the two subsamples as informed by X-ray observations. We find that the two subsamples have the same average halo mass of $1.74\times 10^{14}\, h^{-1}\, \mathrm{M}_{\odot }$, but the concentration of the low-$M_*^{\mathrm{BCG}}$ clusters is $5.87_{-0.60}^{+0.77}$, ∼1.5σ smaller than that of their high-$M_*^{\mathrm{BCG}}$ counterparts ($6.95_{-0.66}^{+0.78}$). Furthermore, both cluster weak lensing and cluster-galaxy cross-correlations indicate that the large-scale bias of the low-$M_*^{\mathrm{BCG}}$, low-concentration clusters are ${\sim}10{{\ \rm per\ cent}}$ higher than that of the high-$M_*^{\mathrm{BCG}}$, high-concentration systems, hence possible evidence of the cluster assembly bias effect. Our results reveal a remarkable physical connection between the stellar mass within $20{-}30\, h^{-1}\, {\mathrm{kpc}}$, the dark matter mass within ${\sim}200\, h^{-1}\, {\mathrm{kpc}}$, and the cosmic overdensity on scales above $10\, h^{-1}\, {\mathrm{Mpc}}$, enabling a key observational test of theories of co-evolution between massive clusters and their central galaxies.
ABSTRACT
We report the non-thermal pressure fraction (Pnt/Ptot) obtained from a three-dimensional triaxial analysis of 16 galaxy clusters in the CLASH sample using gravitational lensing (GL) data ...primarily from Subaru and HST, X-ray spectroscopic imaging from Chandra, and Sunyaev–Zel’dovich effect (SZE) data from Planck and Bolocam. Our results span the approximate radial range 0.015–0.4 R200m (∼35–1000 kpc). At cluster-centric radii smaller than 0.1 R200m the ensemble average Pnt/Ptot is consistent with zero with an upper limit of 9 per cent, indicating that heating from active galactic nuclei and other relevant processes does not produce significant deviations from hydrostatic equilibrium (HSE). The ensemble average Pnt/Ptot increases outside of this radius to approximately 20 per cent at 0.4 R200m, as expected from simulations, due to newly accreted material thermalizing via a series of shocks. Also in agreement with simulations, we find significant cluster-to-cluster variation in Pnt/Ptot and little difference in the ensemble average Pnt/Ptot based on dynamical state. We conclude that on average, even for diverse samples, HSE-derived masses in the very central regions of galaxy clusters require only modest corrections due to non-thermal motions.
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