Sunyaev-Zel’dovich clusters in Millennium gas simulations

Abstract

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.

Cosmological simulations of galaxy clusters with feedback from active galactic nuclei: profiles and scaling relations

“…For our full sample presented here, we use equation (12) to re-scale the profiles for individual clusters before fitting the GNFW model to our median profile and comparing with the observed fits for P 0 = P 3 . It is immediately apparent that the largest contribution to Y SZ occurs around r 500 , far away from the complex physics in the cluster core (Kay et al 2012). At these large radii, there is only a small increase in the pressure when going from CSF→SFB→AGN, suggesting that the Y SZ parameter is reasonably insensitive to the physical model used.…”

CoMaLit – IV. Evolution and self-similarity of scaling relations with the galaxy cluster mass

“…The consensus from numerical simulations is that the YSZ-M∆ is approximately self-similar in mass (1.6 < ∼ β < ∼ 1.8) and it is characterised by a small intrinsic scatter (Stanek et al 2010;Kay et al 2012;Battaglia et al 2012). Stanek et al (2010) found that the evolution with redshift might be negative (γz ∼ −0.34) in presence of cooling and preheating.…”

Covariance in the thermal SZ–weak lensing mass scaling relation of galaxy clusters

“…The simulation volume has a comoving box length of 500 h −1 Mpc, resolved using a uniform 512 3 root grid and 8 levels of mesh refinement, implying a maximum comoving spatial resolution of 3.8 h −1 kpc. While the effects of baryonic physics, such as radiative gas cooling, star formation and energy feedback from supernovae and active galactic nuclei are important in the cluster core regions (r < ∼ 0.15R500c), these additional physics are shown to have negligible ( 2%) impact on the scatter in the tSZ-mass scaling relation (Nagai 2006;Battaglia et al 2012;Kay et al 2012). In Section 5, we assess the impact of baryonic physics with the Omega500 simulation that includes radiative cooling, star formation, and supernova feedback.…”

“…These baryonic physics can in principle induce additional scatter in the observed Y2D −M2D relation by changing the level of gas pressure in the correlated structure along the line of sight. While these effects are expected to be small (Nagai 2006;Battaglia et al 2012;Kay et al 2012), further scrutiny is still useful in order to assess to what extent the impact of the uncertain baryonic physics on the Y2D − M2D relation.…”

“…Numerical simulations predict that the tSZ effect signal is a robust proxy of cluster mass with intrinsic scatter of 10% as it directly probes the thermal energy content of the virialized ICM (e.g., Motl et al 2005;Nagai 2006;Kay et al 2012;Sembolini et al 2013;Yu, Nelson & Nagai 2015).…”