We present an implementation of stellar evolution and chemical feedback for smoothed particle hydrodynamics simulations. We consider the timed release of individual elements by both massive (Type II supernovae and stellar winds) and intermediate‐mass stars (Type Ia supernovae and asymptotic giant branch stars). We illustrate the results of our method using a suite of cosmological simulations that include new prescriptions for radiative cooling, star formation and galactic winds. Radiative cooling is implemented element‐by‐element, in the presence of an ionizing radiation background, and we track all 11 elements that contribute significantly to the radiative cooling. While all simulations presented here use a single set of physical parameters, we take specific care to investigate the robustness of the predictions of chemodynamical simulations with respect to the ingredients, the methods and the numerical convergence. A comparison of nucleosynthetic yields taken from the literature indicates that relative abundance ratios may only be reliable at the factor of 2 level, even for a fixed initial mass function. Abundances relative to iron are even more uncertain because the rate of Type Ia supernovae is not well known. We contrast two reasonable definitions of the metallicity of a resolution element and find that while they agree for high metallicities, there are large differences at low metallicities. We argue that the discrepancy is indicative of the lack of metal mixing caused by the fact that metals are stuck to particles. We argue that since this is a (numerical) sampling problem, solving it by using a poorly constrained physical process such as diffusion could have undesired consequences. We demonstrate that the two metallicity definitions result in redshift z= 0 stellar masses that can differ by up to a factor of 2, because of the sensitivity of the cooling rates to the elemental abundances. Finally, we use several 5123 particle simulations to investigate the evolution of the distribution of heavy elements, which we find to be in reasonably good agreement with available observational constraints. We find that by z= 0 most of the metals are locked up in stars. The gaseous metals are distributed over a very wide range of gas densities and temperatures. The shock‐heated warm–hot intergalactic medium has a relatively high metallicity of ∼10−1 Z⊙ that evolves only weakly, and is therefore an important reservoir of metals. Any census aiming to account for most of the metal mass will have to take a wide variety of objects and structures into account.

We present results on the X-ray properties of clusters and groups of galaxies, extracted from a large cosmological hydrodynamical simulation. We used the TREE+SPH code GADGET to simulate a concordance Λ cold dark matter cosmological model within a box of 192 h-1 Mpc on a side, 4803 dark matter particles and as many gas particles. The simulation includes radiative cooling assuming zero metallicity, star formation and supernova feedback. The very high dynamic range of the simulation allows us to cover a fairly large interval of cluster temperatures. We compute X-ray observables of the intracluster medium (ICM) for simulated groups and clusters and analyse their statistical properties. The simulated mass-temperature relation is consistent with observations once we mimic the procedure for mass estimates applied to real clusters. Also, with the adopted choices of Ωm= 0.3 and σ8= 0.8 for matter density and power spectrum normalization, respectively, the resulting X-ray temperature function agrees with the most recent observational determinations. The luminosity-temperature relation also agrees with observations for clusters with T>~ 2 keV. At the scale of groups, T<~ 1 keV, we find no change of slope in this relation. The entropy in central cluster regions is higher than predicted by gravitational heating alone, the excess being almost the same for clusters and groups. We also find that the simulated clusters appear to have suffered some overcooling. We find f*~= 0.2 for the fraction of baryons in stars within clusters, thus approximately twice as large as the value observed. Interestingly, temperature profiles of simulated clusters are found to increase steadily toward cluster centres. They decrease in the outer regions, much like observational data do at r>~ 0.2rvir, while not showing an isothermal regime followed by a smooth temperature decline in the innermost regions. Our results thus demonstrate the need for yet more efficient sources of energy feedback and/or the need to consider additional physical process which may be able to further suppress the gas density at the scale of poor clusters and groups, and, at the same time, to regulate the cooling of the ICM in central regions

We present cosmological hydrodynamical simulations of galaxy clusters aimed at studying the process of metal enrichment of the intra-cluster medium (ICM). These simulations have been performed by implementing a detailed model of chemical evolution in the TREE-PM+SPMGADGET-2 code. This model allows us to follow the metal release from Type II supernovae (SNII), Type Ia supernovae (SNIa) and asymptotic giant branch (AGB) stars by properly accounting for the lifetimes of stars of different mass, as well as to change the stellar initial mass function (IMF), the lifetime function and the stellar yields. As such, our implementation of chemical evolution represents a powerful instrument to follow the cosmic history of metal production. The simulations presented here have been performed with the twofold aim of checking numerical effects, as well as the impact of changing the model of chemical evolution and the efficiency of stellar feedback. In general, we find that the distribution of metals produced by SNII is more clumpy than for the product of low-mass stars, as a consequence of the different time-scales over which they are released. Using a standard Salpeter IMF produces a radial profile of iron abundance which is in fairly good agreement with observations available out to ~=0.6R500. This result holds almost independent of the numerical scheme adopted to distribute metals around star-forming regions. The mean age of enrichment of the ICM corresponds to redshift z ~ 0.5, which progressively increases outside the virial region. Increasing resolution, we improve the description of a diffuse high-redshift enrichment of the inter-galactic medium (IGM). This turns into a progressively more efficient enrichment of the cluster outskirts, while having a smaller impact at R <~ 0.5R500. As for the effect of the model of chemical evolution, we find that changing the IMF has the strongest impact. Using an IMF, which is top-heavier than the Salpeter one, provides a larger iron abundance, possibly in excess of the observed level, also significantly increasing the [O/Fe] relative abundance. Our simulations always show an excess of low-redshift star formation and, therefore, of the abundance of oxygen in central cluster regions, at variance with observations. This problem is not significantly ameliorated by increasing the efficiency of the stellar feedback

We present a study of the effect of active galactic nuclei (AGN) feedback on metal enrichment and thermal properties of the intracluster medium (ICM) in hydrodynamical simulations of galaxy clusters. The simulations are performed using a version of the TreePM–sphgadget‐2 code, which also follows chemodynamical evolution by accounting for metal enrichment contributed by different stellar populations. We carry out cosmological simulations for a set of galaxy clusters, covering the mass range M200≃ (0.1–2.2) × 1015 h−1 M⊙. Besides runs not including any efficient form of energy feedback, we carry out simulations including three different feedback schemes: (i) kinetic feedback in the form of galactic winds triggered by supernova explosions; (ii) AGN feedback from gas accretion on to supermassive black holes (BHs) and (iii) AGN feedback in which a ‘radio mode’ is included with an efficient thermal coupling of the extracted energy, whenever BHs enter in a quiescent accretion phase. Besides investigating the resulting thermal properties of the ICM, we analyse in detail the effect that these feedback models have on the ICM metal enrichment. We find that AGN feedback has the desired effect of quenching star formation in the brightest cluster galaxies at z < 4 and provides correct temperature profiles in the central regions of galaxy groups. However, its effect is not yet sufficient to create ‘cool cores’ in massive clusters while generating an excess of entropy in central regions of galaxy groups. As for the pattern of metal distribution, AGN feedback creates a widespread enrichment in the outskirts of clusters, thanks to its efficiency in displacing enriched gas from galactic haloes to the intergalactic medium. This turns into profiles of iron abundance, ZFe, which are in better agreement with observational results, and into a more pristine enrichment of the ICM around and beyond the cluster virial regions. Following the pattern of the relative abundances of silicon and iron, we conclude that a significant fraction of the ICM enrichment is contributed in simulations by a diffuse population of intracluster stars. Our simulations also predict that profiles of the ZSi/ZFe abundance ratio do not increase at increasing radii, at least out to 0.5Rvir. Our results clearly show that different sources of energy feedback leave distinct imprints in the enrichment pattern of the ICM. They further demonstrate that such imprints are more evident when looking at external regions, approaching the cluster virial boundaries.

We present results from the first cosmological simulations which study the onset of primordial, metal-free (population III), cosmic star formation and the transition to the present-day, metal-rich star formation (population II-I), including molecular (H$_2$, HD, etc.) evolution, tracing the injection of metals by supernov{\ae} into the surrounding intergalactic medium and following the change in the initial stellar mass function (IMF) according to the metallicity of the corresponding stellar population. Our investigation addresses the role of a wide variety of parameters (critical metallicity for the transition, IMF slope and range, SN/pair-instability SN metal yields, star formation threshold, resolution, etc.) on the metal-enrichment history and the associated transition in the star formation mode. All simulations present common trends. Metal enrichment is very patchy, with rare, unpolluted regions surviving at all redshifts, inducing the simultaneous presence of metal-free and metal-rich star formation regimes. As a result of the rapid pollution within high-density regions due to the first SN/pair-instability SN, local metallicity is quickly boosted above the critical metallicity for the transition. The population III regime lasts for a very short period during the first stages of star formation ($\sim 10^7\,\rm yr$), and its average contribution to the total star formation rate density drops rapidly below $\sim 10^{-3}-10^{-2}$

A Population III/Population II transition from massive to normal stars is predicted to occur when the metallicity of the star-forming gas crosses the critical range Zcr = 10-5+/-1Zsolar. To investigate the cosmic implications of such a process, we use numerical simulations which follow the evolution, metal enrichment and energy deposition of both Population II and Population III stars. We find that: (i) due to inefficient heavy element transport by outflows and slow `genetic' transmission during hierarchical growth, large fluctuations around the average metallicity arise; as a result, Population III star formation continues down to z = 2.5, but at a low peak rate of 10-5Msolaryr-1Mpc-3 occurring at z ~ 6 (about 10-4 of the Population II one); and (ii) Population III star formation proceeds in an `inside-out' mode in which formation sites are progressively confined to the periphery of collapsed structures, where the low gas density and correspondingly long free-fall time-scales result in a very inefficient astration. These conclusions strongly encourage deep searches for pristine star formation sites at moderate (2 < z < 5) redshifts where metal-free stars are likely to be hidden

We study the properties of the diffuse light in galaxy clusters forming in a large hydrodynamical cosmological simulation of the L cold dark matter cosmology. The simulation includes a model for radiative cooling, star formation in dense cold gas, and feedback by Type II supernova explosions. We select clusters having mass 14 Ϫ1M 1 10 h M , and study the spatial distribution of their star particles. While most stellar light is concentrated in gravitationally bound galaxies orbiting in the cluster potential, we find evidence for a substantial diffuse component, which may account for the extended halos of light observed around central cD galaxies. We find that more massive simulated clusters have a larger fraction of stars in the diffuse light than the less massive ones. The intracluster light is more centrally concentrated than the galaxy light, and the stars in the diffuse component are on average older than the stars in cluster galaxies, supporting the view that the diffuse light is not a random sampling of the stellar population in the cluster galaxies. We thus expect that at least ∼10% of the stars in a cluster may be distributed as intracluster light, largely hidden thus far because of its very low surface brightness.

We carry out an analysis of a set of cosmological SPH hydrodynamical simulations of galaxy clusters and groups aimed at studying the total baryon budget in clusters, and how this budget is shared between the hot diffuse component and the stellar component. Using the TreePM+SPH GADGET-3 code, we carried out one set of non-radiative simulations, and two sets of simulations including radiative cooling, star formation and feedback from supernovae (SN), one of which also accounting for the effect of feedback from active galactic nuclei (AGN). The analysis is carried out with the twofold aim of studying the implication of stellar and hot gas content on the relative role played by SN and AGN feedback, and to calibrate the cluster baryon fraction and its evolution as a cosmological tool. With respect to previous similar analysis, the simulations used in this study provide us with a sufficient statistics of massive objects and including an efficient AGN feedback. We find that both radiative simulation sets predict a trend of stellar mass fraction with cluster mass that tends to be weaker than the observed one. However this tension depends on the particular set of observational data considered. Including the effect of AGN feedback alleviates this tension on the stellar mass and predicts values of the hot gas mass fraction and total baryon fraction to be in closer agreement with observational results. We further compute the ratio between the cluster baryon content and the cosmic baryon fraction, Y b , as a function of cluster-centric radius and redshift. At R 500 we find for massive clusters with M 500 > 2 × 10 14 h −1 M ⊙ that Y b is nearly independent of the physical processes included and characterized by a negligible redshift evolution: Y b,500 = 0.85 ± 0.03 with the error accounting for the intrinsic r.m.s. scatter within the set of simulated clusters. At smaller radii, R 2500 , the typical value of Y b slightly decreases, by an amount that depends on the physics included in the simulations, while its scatter increases by about a factor of two. These results have interesting implications for the cosmological applications of the baryon fraction in clusters.