The XMM Cluster Survey (XCS) is a serendipitous search for galaxy clusters using all publicly available data in the XMM–Newton Science Archive. Its main aims are to measure cosmological parameters and trace the evolution of X‐ray scaling relations. In this paper we present the first data release from the XMM Cluster Survey (XCS‐DR1). This consists of 503  optically confirmed, serendipitously detected, X‐ray clusters. Of these clusters, 256  are new to the literature and 357  are new X‐ray discoveries. We present 463  clusters with a redshift estimate (0.06 < z < 1.46), including 261  clusters with spectroscopic redshifts. The remainder have photometric redshifts. In addition, we have measured X‐ray temperatures (TX) for 401  clusters (0.4 < TX < 14.7 keV). We highlight seven interesting subsamples of XCS‐DR1 clusters: (i) 10  clusters at high redshift (z > 1.0, including a new spectroscopically confirmed cluster at z= 1.01); (ii) 66  clusters with high TX (>5 keV); (iii) 130  clusters/groups with low TX (<2 keV); (iv) 27  clusters with measured TX values in the Sloan Digital Sky Survey (SDSS) ‘Stripe 82’ co‐add region; (v) 77  clusters with measured TX values in the Dark Energy Survey region; (vi) 40  clusters detected with sufficient counts to permit mass measurements (under the assumption of hydrostatic equilibrium); (vii) 104  clusters that can be used for applications such as the derivation of cosmological parameters and the measurement of cluster scaling relations. The X‐ray analysis methodology used to construct and analyse the XCS‐DR1 cluster sample has been presented in a companion paper, Lloyd‐Davies et al.

We use numerical simulations to investigate, for the first time, the joint effect of feedback from supernovae (SNe) and active galactic nuclei (AGN) on the evolution of galaxy cluster X-ray scaling relations. Our simulations are drawn from the Millennium Gas Project and are some of the largest hydrodynamical N-body simulations ever carried out. Feedback is implemented using a hybrid scheme, where the energy input into intracluster gas by SNe and AGN is taken from a semi-analytic model of galaxy formation. This ensures that the source of feedback is a population of galaxies that closely resembles that found in the real universe. We show that our feedback model is capable of reproducing observed local X-ray scaling laws, at least for non-cool core clusters, but that almost identical results can be obtained with a simplistic preheating model. However, we demonstrate that the two models predict opposing evolutionary behaviour. We have examined whether the evolution predicted by our feedback model is compatible with observations of high-redshift clusters. Broadly speaking, we find that the data seems to favour the feedback model for z<0.5, and the preheating model at higher redshift. However, a statistically meaningful comparison with observations is impossible, because the large samples of high-redshift clusters currently available are prone to strong selection biases. As the observational picture becomes clearer in the near future, it should be possible to place tight constraints on the evolution of the scaling laws, providing us with an invaluable probe of the physical processes operating in galaxy clusters.Comment: 23 pages, 14 figures, 3 tables. Minor revisons in line with referee's comments. Published in MNRA

Large surveys using the Sunyaev–Zel’dovich (SZ) effect to find clusters of galaxies are now starting to yield large numbers of systems out to high redshift, many of which are new discoveries. In order to provide theoretical interpretation for the release of the full SZ cluster samples over the next few years, we have exploited the large‐volume Millennium gas cosmological N‐body hydrodynamics simulations to study the SZ cluster population at low and high redshift, for three models with varying gas physics. We confirm previous results using smaller samples that the intrinsic (spherical) Y500–M500 relation has very little scatter (), is insensitive to cluster gas physics and evolves to redshift 1 in accordance with self‐similar expectations. Our preheating and feedback models predict scaling relations that are in excellent agreement with the recent analysis from combined Planck and XMM–Newton data by the Planck Collaboration. This agreement is largely preserved when r500 and M500 are derived using the hydrostatic mass proxy, YX, 500, albeit with significantly reduced scatter (), a result that is due to the tight correlation between Y500 and YX, 500. Interestingly, this assumption also hides any bias in the relation due to dynamical activity. We also assess the importance of projection effects from large‐scale structure along the line of sight, by extracting cluster Y500 values from 50 simulated 5 × 5‐deg2 sky maps. Once the (model‐dependent) mean signal is subtracted from the maps we find that the integrated SZ signal is unbiased with respect to the underlying clusters, although the scatter in the (cylindrical) Y500–M500 relation increases in the preheating case, where a significant amount of energy was injected into the intergalactic medium at high redshift. Finally, we study the hot gas pressure profiles to investigate the origin of the SZ signal and find that the largest contribution comes from radii close to r500 in all cases. The profiles themselves are well described by generalized Navarro, Frenk & White profiles but there is significant cluster‐to‐cluster scatter. In conclusion, our results support the notion that Y500 is a robust mass proxy for use in cosmological analyses with clusters.

The Millennium Gas Project aims to undertake smoothed particle hydrodynamic resimulations of the millennium simulation, providing many hundred massive galaxy clusters for comparison with X-ray surveys (170 clusters with kT sl > 3 keV). This paper looks at the hot gas and stellar fractions of clusters in simulations with different physical heating mechanisms. These fail to reproduce cool-core systems but are successful in matching the hot gas profiles of noncool-core clusters. Although there is immense scatter in the observational data, the simulated clusters broadly match the integrated gas fractions within r 500 . In line with previous work, however, they fare much less well when compared to the stellar fractions, having a dependence on cluster mass that is much weaker than is observed. The evolution with redshift of the hot gas fraction is much larger in the simulation with early pre-heating than in one with continual feedback; observations favour the latter model. The strong dependence of hot gas fraction on cluster physics limits its use as a probe of cosmological parameters.

We present numerical simulations of galaxy clusters with stochastic heating from active galactic nuclei (AGN) that are able to reproduce the observed entropy and temperature profiles of non-cool-core (NCC) clusters. Our study uses N -body hydrodynamical simulations to investigate how star formation, metal production, black hole accretion, and the associated feedback from supernovae and AGN, heat and enrich diffuse gas in galaxy clusters. We assess how different implementations of these processes affect the thermal and chemical properties of the intracluster medium (ICM), using high-quality X-ray observations of local clusters to constrain our models. For the purposes of this study we have resimulated a sample of 25 massive galaxy clusters extracted from the Millennium Simulation. Sub-grid physics is handled using a semi-analytic model of galaxy formation, thus guaranteeing that the source of feedback in our simulations is a population of galaxies with realistic properties. We find that supernova feedback has no effect on the entropy and metallicity structure of the ICM, regardless of the method used to inject energy and metals into the diffuse gas. By including AGN feedback, we are able to explain the observed entropy and metallicity profiles of clusters, as well as the X-ray luminosity-temperature scaling relation for NCC systems. A stochastic model of AGN energy injection motivated by anisotropic jet heating -presented for the first time here -is crucial for this success.With the addition of metal-dependent radiative cooling, our model is also able to produce CC clusters, without over-cooling of gas in dense, central regions.