On the cluster physics of Sunyaev–Zel’dovich and X-ray surveys. IV. Characterizing density and pressure clumping due to infalling substructures
- McWilliams Center for Cosmology, Carnegie Mellon University, Department of Physics, 5000 Forbes Ave., Pittsburgh PA, 15213 (United States)
- Canadian Institute for Theoretical Astrophysics, 60 St George, Toronto ON, M5S 3H8 (Canada)
- Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, D-69118 Heidelberg (Germany)
Understanding the outskirts of galaxy clusters at the virial radius (R{sub 200}) and beyond is critical for an accurate determination of cluster masses, structure growth, and to ensure unbiased cosmological parameter estimates from cluster surveys. This problem has drawn renewed interest due to recent determinations of gas mass fractions beyond R{sub 200}, which appear to be considerably larger than the cosmic mean. Here, we use a large suite of cosmological hydrodynamical simulations to study the inhomogeneity of the intra-cluster medium and employ different variants of simulated physics, including radiative gas physics and thermal feedback by active galactic nuclei. We find that density and pressure clumping closely trace each other as a function of radius, but the bias on density remains on average <20% within R{sub 200}. At larger radii, clumping increases steeply due to the continuous infall of coherent structures that have not yet passed the accretion shock. Density and pressure clumping increase with cluster mass and redshift, which probes on average dynamically younger objects that are still in the process of assembling. The angular power spectra of gas density and pressure show that the clumping signal is dominated by large-scale cosmic filaments that reach from the cosmic web into the clusters, signaling the presence of gravitationally driven “super clumping.” While the prolateness of the gravitational halo potential implies an approximate radial correlation of these gaseous large-scale structures, gas density and pressure lose coherence on small scales across different radii due to dissipative gas physics. In contrast, the angular power spectrum of dark matter shows an almost uniform size distribution due to unimpeded subhalos. We provide a synopsis of the radial dependence of the clusters’ non-equilibrium measures (kinetic pressure support, ellipticity, and clumping) that all increase sharply beyond R{sub 200}.
- OSTI ID:
- 22883107
- Journal Information:
- Astrophysical Journal, Vol. 806, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
Similar Records
Witnessing the growth of the nearest galaxy cluster: thermodynamics of the Virgo Cluster outskirts
DECONSTRUCTING THERMAL SUNYAEV–ZEL’DOVICH—GRAVITATIONAL LENSING CROSS-CORRELATIONS: IMPLICATIONS FOR THE INTRACLUSTER MEDIUM