Effect of primordial non-Gaussianities on galaxy clusters scaling relations

Abstract

Galaxy clusters are a valuable source of cosmological information. Their formation and evolution depends on the underlying cosmology and on the statistical nature of the primordial density fluctuations. In this work we investigate the impact of primordial non-gaussianities (PNG) on the scaling properties of galaxy clusters. We performed a series of cosmological hydrodynamic N-body simulations featuring adiabatic gas physics and different levels of nonGaussian initial conditions within the ΛCDM framework. We focus on the T −M, S −M, Y −M and Y X − M scalings relating the total cluster mass with temperature, entropy and SZ cluster integrated pressure that reflect the thermodynamical state of the intra-cluster medium. Our results show that PNG have an impact on cluster scalings laws. The mass power-law indexes of the scalings are almost unaffected by the existence of PNG but the amplitude and redshift evolution of their normalizations are clearly affected. The effect is stronger for the evolution of the Y − M and Y X − M normalizations, which change by as much as 22% and 16% when f NL varies from −500 to 500, respectively. These results are consistent with the view that positive/negative f NL affect cluster profiles due to an increase/decrease of cluster concentrations. At low values of f NL , as suggested by present Planck constraints on a scale invariant f NL , the impact on the scalings normalizations is only a few percent, which is small when compared with the effect of additional gas physics and other cosmological effects such as dark energy. However if f NL is in fact a scale dependent parameter, PNG may have larger positive/negative amplitudes at clusters scales and therefore our results suggest that PNG should be taken into account when galaxy cluster data is used to infer cosmological parameters or to asses the constraining power of future cluster surveys.

Unveiling the Dynamics of the Universe

“…Hydrodynamic N-body simulations are the appropriate method to study galaxy cluster scaling relations as they allow us to model the baryon physics throughout the full non-linear evolution of the ICM gas and determine the parameters α, β ss , β and A 0 . We refer the reader to references [274][275][276][277] for examples of simulations studies showing the impact of various gas physical models, dark energy and primordial non-Gaussianities on several galaxy cluster scalings. Numerical N-body simulations have also been intensively used to study the internal structure of galaxy clusters.…”

“…However, this task is not easy, since it is not possible to directly estimate the mass of a galaxy cluster from observational data, and thus one must rely on indirect methods, such as the scaling properties of clusters, to obtain a reliable estimate. The effect of PNG on galaxy clusters scaling relations was investigated for the first time in [277]. The authors resorted to a series of hydrodynamical N-body numerical simulations featuring adiabatic gas physics and allowing for different levels of non-Gaussian initial conditions within the fiducial ΛCDM model.…”

“…In particular they studied the T − M, S − M, Y − M and Y X − M scalings relating the total cluster mass with temperature, entropy and SZ cluster integrated pressure that reflect the thermodynamical state of the intra-cluster medium. Figure 10 shows as an example, the distribution of galaxy clusters for the Y − M, for three different levels of PNG, i.e., f NG ± 500, 0 obtained by [277], while Figure 11 shows the result of fitting Equation (153) for the Y − M scaling to the corresponding distribution of clusters, using the procedure suggested by [276,317]. The main findings of [277], indicate that PNG do have an impact on clusters scaling laws, in particular on the amplitude and redshift evolution of the scalings normalization.…”