Total mass biases in X-ray galaxy clusters

By R. Piffaretti, R. Valdarnini. 2008

169 citations recorded by the source corpus.

Context. The exploitation of clusters of galaxies as cosmological probes relies on accurate measurements of their total gravitating mass. X-ray observations provide a powerful means of probing the total mass distribution in galaxy clusters, but might be affected by observational biases and rely on simplistic assumptions originating from our limited understanding of the intracluster medium physics. Aims. This paper is aimed at elucidating the reliability of X-ray total mass estimates in clusters of galaxies by properly disentangling various biases of both observational and physical origin. Methods. We use N-body/SPH simulation of a large sample of ∼100 galaxy clusters and investigate total mass biases by comparing the mass reconstructed adopting an observational-like approach with the true mass in the simulations. X-ray surface brightness and temperature profiles extracted from the simulations are fitted with different models and adopting different radial fitting ranges in order to investigate modeling and extrapolation biases. Different theoretical definitions of gas temperature are used to investigate the effect of spectroscopic temperatures and a power ratio analysis of the surface brightness maps allows us to assess the dependence of the mass bias on cluster dynamical state. Moreover, we perform a study on the reliability of hydrostatic and hydrodynamical equilibrium mass estimates using the full three-dimensional information in the simulation. Results. A model with a low degree of sophistication such as the polytropic β-model can introduce, in comparison with a more adequate model, an additional mass underestimate of the order of ∼10% at r500 and ∼15% at r200. Underestimates due to extrapolation alone are at most of the order of ∼10% on average, but can be as large as ∼50% for individual objects. Masses are on average biased lower for disturbed clusters than for relaxed ones and the scatter of the bias rapidly increases with increasingly disturbed dynamical state. The bias originating from spectroscopic temperatures alone is of the order of 10% at all radii for the whole numerical sample, but strongly depends on both dynamical state and cluster mass. From the full three dimensional information in the simulations we find that the hydrostatic equilibrium assumption yields masses underestimated by ∼10–15% and that masses computed by means of the hydrodynamical estimator are unbiased. Finally, we show that there is excellent agreement between our findings, results from similar analyses based on both Eulerian and Lagrangian simulations, and recent observational work based on the comparison between X-ray and gravitational lensing mass estimates.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/5ae0c7d67530bb3c8a56daa59391aab9dc54c86a

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Citations in the corpus

RESIDUAL GAS MOTIONS IN THE INTRACLUSTER MEDIUM AND BIAS IN HYDROSTATIC MEASUREMENTS OF MASS PROFILES OF CLUSTERS (2009, background): “…agreement with previous studies (Evrard 1990; Frenk et al. 1999; Rasia et al. 2004; Faltenbacher et al. 2005; Rasia et al. 2006; Nagai et al. 2007b; Piffaretti & Valdarnini 2008; Jeltema et al. 2008; Iapichino & Niemeyer 2008), we find that gas motions contribute up to≈ 5%−15% of the pressure…”
Formation of Galaxy Clusters (2012, methodology): “…from equilibrium affect observable properties of clusters and cause systematic errors when equations 9 and 10 are used to estimate cluster masses (e.g., Ameglio et al. 2009; Lau, Kravtsov & Nagai 2009; Nagai, Kravtsov & Vikhlinin 2007; Piffaretti & Valdarnini 2008; Rasia, Tormen & Moscardini 2004).”
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).”
Lensing and x-ray mass estimates of clusters (simulations) (2012, methodology): “The best fit values are similar to those found by Jeltema et al. (2008) and Piffaretti & Valdarnini (2008).”
The MCXC: a meta-catalogue of x-ray detected clusters of galaxies (2010, background): “…has also been made in understanding the systematics affecting X-ray mass estimates via simulations (e.g., Rasia et al. 2006; Nagai et al. 2007a; Piffaretti & Valdarnini 2008) and via combination with gravitational lensing (e.g., Mahdavi et al. 2008; Zhang et al. 2010; Meneghetti et al. 2010).”
IMPACT OF CLUSTER PHYSICS ON THE SUNYAEV–ZEL'DOVICH POWER SPECTRUM (2010, background): “A10 found there to be a good agreement between the observed profiles and those measured from the hydrodynamical simulations of Borgani et al. (2004); Nagai et al. (2007a) and Piffaretti & Valdarnini (2008).”
The universal galaxy cluster pressure profile from a representative sample of nearby systems (REXCESS) and the Y-SZ-M-500 relation (2009, methodology): “As in previous work (e.g., Piffaretti & Valdarnini 2008, and references therein), we find thatMHSE500 underestimates the true mass.”
Planck 2013 results. XX. Cosmology from Sunyaev-Zeldovich cluster counts (2013, background): “…to underestimate the true mass by 10–15 percent due to neglect of bulk motions and turbulence in the intra-cluster medium (ICM, e.g., Nagai et al. 2007; Piffaretti & Valdarnini 2008; Meneghetti et al. 2010), an effect that is commonly referred to in the literature as the “hydrostatic mass bias”.”