RESIDUAL GAS MOTIONS IN THE INTRACLUSTER MEDIUM AND BIAS IN HYDROSTATIC MEASUREMENTS OF MASS PROFILES OF CLUSTERS

By E. Lau, Andrey V. Kravtsov, D. Nagai. 2009

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We present analysis of bulk and random gas motions in the intracluster medium using high-resolution Eulerian cosmological simulations of 16 simulated clusters, including both very relaxed and unrelaxed systems and spanning a virial mass range of 5 × 1013–. We investigate effects of the residual subsonic gas motions on the hydrostatic estimates of mass profiles and concentrations of galaxy clusters. In agreement with previous studies, we find that the gas motions contribute up to ≈5%–15% of the total pressure support in relaxed clusters with contribution increasing with the cluster-centric radius. The fractional pressure support is higher in unrelaxed systems. This contribution would not be accounted for in hydrostatic estimates of the total mass profile and would lead to systematic underestimate of mass. We demonstrate that total mass can be recovered accurately if pressure due to gas motions measured in simulations is explicitly taken into account in the equation of hydrostatic equilibrium. Given that the underestimate of mass is increasing at larger radii, where gas is less relaxed and contribution of gas motions to pressure is larger, the total density profile derived from hydrostatic analysis is more concentrated than the true profile. This may at least partially explain some high values of concentrations of clusters estimated from hydrostatic analysis of X-ray data.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering, Instrumentation

View Paper: https://www.semanticscholar.org/paper/4c055487a48a2541827acf867d8c3b1403cde0cf

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Citations in the corpus

Weighing simulated galaxy clusters using lensing and X-ray (2009, background): “It was proposed that X-ray masses could be systematically biased because of mergers or bulk motions of the gas that alter the state of hydrostatic equilibrium (Bartelmann & Steinmetz 1996; Allen 1998; Mahdavi et al. 2008; Piffaretti & Valdarnini 2008; Ameglio et al. 2009; Lau et al. 2009).”
JOINT ANALYSIS OF CLUSTER OBSERVATIONS. II. CHANDRA/XMM-NEWTON X-RAY AND WEAK LENSING SCALING RELATIONS FOR A SAMPLE OF 50 RICH CLUSTERS OF GALAXIES (2012, background): “…tend to underestimate the true mass by 10%–20% was first discussed by Evrard (1990) and continues to be important in grid-based simulations (e.g., Lau et al. 2009; Nelson et al. 2012), SPH simulations (e.g., Rasia et al. 2006; Battaglia et al. 2012; Rasia et al. 2012), and observations of…”
DARK MATTER HALO PROFILES OF MASSIVE CLUSTERS: THEORY VERSUS OBSERVATIONS (2011, background): “For example, the lensing data need to account for bias due to the triaxiality of halos while the X-ray data typically ignore the non-thermal pressure component in galaxy clusters which can lead to a systematic underestimate of the cluster mass (Lau et al. 2009).”
ON THE CLUSTER PHYSICS OF SUNYAEV–ZEL'DOVICH AND X-RAY SURVEYS. I. THE INFLUENCE OF FEEDBACK, NON-THERMAL PRESSURE, AND CLUSTER SHAPES ON Y–M SCALING RELATIONS (2011, methodology): “Including the support from residual gas motions in the hydrostatic cluster mass estimator improved the match with the true cluster mass (Rasia et al. 2004), with increasing kinetic pressure at larger cluster radii (Lau et al. 2009).”
CLASH-VLT: The mass, velocity-anisotropy, and pseudo-phase-space density profiles of the z = 0.44 galaxy cluster MACS J1206.2-0847 (2013, background): “For instance, X-ray determinations of cluster masses tend to be underestimated if bulk gas motions and the complex thermal structure of the Intra-Cluster Medium (ICM) are ignored (Rasia et al. 2004, 2006; Lau et al. 2009; Molnar et al. 2010; Cavaliere et al. 2011).”
Shocking results without shocks: Subsonic turbulence in smoothed particle hydrodynamics and moving-mesh simulations (2011, background): “…or even higher contributions of the kinetic energy in turbulence relative to the thermal energy in the ICM (Iapichino & Niemeyer 2008; Vazza et al. 2009; Maier et al. 2009; Lau et al. 2009; Vazza et al. 2011; Paul et al. 2011; Schmidt & Federrath 2011; Iapichino et al. 2011; Jones et al. 2011).”
IMPACT OF CLUSTER PHYSICS ON THE SUNYAEV–ZEL'DOVICH POWER SPECTRUM (2010, methodology): “The blue point represents the mean MHSE500 /M500 measured from the Lau et al. (2009) simulated clusters, with the error bar representing the error on the mean.”
Planck 2013 results. XX. Cosmology from Sunyaev-Zeldovich cluster counts (2013, background): “The majority of numerical simulations predict HE biases of 10 to 20 percent (Nagai et al. 2007; Piffaretti & Valdarnini 2008; Lau et al. 2009; Kay et al. 2012; Rasia et al. 2012).”
Massive and refined - II. The statistical properties of turbulent motions in massive galaxy clusters with high spatial resolution (2010, methodology): “This has been done for instance by taking spherical shell averages (e.g. Bryan & Norman 1999; Iapichino & Niemeyer 2008; Lau et al.2009; Burns et al.2010), by mapping in 3–”
MASSIVE HALOS IN MILLENNIUM GAS SIMULATIONS: MULTIVARIATE SCALING RELATIONS (2009, background): “While the dark matter virial scaling is robust to simple physical treatments for the baryons, (Lau et al. 2009) find that strongly dissipative baryon physics depresses the slope of the σDM − M relation by introducing mass- and redshift-dependent increases in halo velocity dispersion.”
X-RAY PROPERTIES OF THE FIRST SUNYAEV–ZEL'DOVICH EFFECT SELECTED GALAXY CLUSTER SAMPLE FROM THE SOUTH POLE TELESCOPE (2010, background): “Numerical simulations have suggested that hydrostatic mass estimates could be biased low by ∼10% due to additional non-thermal pressure support of the gas in clusters (e.g., Lau et al. 2009; Meneghetti et al. 2010).”
LOCATING THE “MISSING” BARYONS WITH EXTRAGALACTIC DISPERSION MEASURE ESTIMATES (2013, background): “Simulations find M ∼ 0.1–0.2 at <2rvir for halos with mh ∼ 1015 M (Lau et al. 2009), and it is likely that similar Mach numbers apply at lower mh.”
GALAXY CLUSTERS SELECTED WITH THE SUNYAEV–ZEL'DOVICH EFFECT FROM 2008 SOUTH POLE TELESCOPE OBSERVATIONS (2010, methodology): “The mass dependence of their pressure profile was determined using cluster mass estimates derived from the equation of hydrostatic equilibrium; simulations suggest that this method may underestimate the true mass by 10%–20% (Rasia et al. 2004; Meneghetti et al. 2010; Lau et al. 2009).”
THE DENSITY PROFILES OF MASSIVE, RELAXED GALAXY CLUSTERS. I. THE TOTAL DENSITY OVER THREE DECADES IN RADIUS (2012, background): “Mock observations of simulated clusters show that to a remarkable degree, X-ray observations are able to recover spherically-averaged mass profiles with a scatter of only ' 5%−10% (Nagai et al. 2007; Lau et al. 2009; Meneghetti et al. 2010b; Rasia et al. 2012).”