Comparing the temperatures of galaxy clusters from hydrodynamical N-body simulations to Chandra and XMM-Newton observations

By P. Mazzotta, E. Rasia, L. Moscardini, G. Tormen, Department of Physics University of RomeTor Vergata, I. Astrophysics, U. D. D. Astronomia, U. Padova, I. D. D. Astronomia, U. Bologna and 1 more. 2004

307 citations recorded by the source corpus.

Theoretical studies of the physical processes guiding the formation and evolution of galaxies and galaxy clusters in the X-ray region are mainly based on the results of numerical hydrodynamical N-body simulations, which in turn are often directly compared with X-ray observations. Although trivial in principle, these comparisons are not always simple. We demonstrate that the projected spectroscopic temperature of thermally complex clusters obtained from X-ray observations is always lower than the emission-weighed temperature, which is widely used in the analysis of numerical simulations. We show that this temperature bias is mainly related to the fact that the emission-weighted temperature does not reflect the actual spectral properties of the observed source. This has important implications for the study of thermal structures in clusters, especially when strong temperature gradients, such as shock fronts, are present. Because of this bias, in real observations shock fronts appear much weaker than what is predicted by emission-weighted temperature maps, and may not even be detected. This may explain why, although numerical simulations predict that shock fronts are a quite common feature in clusters of galaxies, to date there are very few observations of objects in which they are clearly seen. To fix this problem we propose a new formula, the spectroscopic-like temperature function, and show that, for temperatures higher than 3 keV, it approximates the spectroscopic temperature to better than a few per cent, making simulations more directly comparable to observations.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/1ab466b7af5a42eb694d10ce06a257007ca468f5

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Citations in the corpus

The case for AGN feedback in galaxy groups (2009, background): “The emission-weighted temperature differs from the Mazzotta et al. (2004) definition of “spectroscopic” temperature typically by only 10%.”
MASSIVE HALOS IN MILLENNIUM GAS SIMULATIONS: MULTIVARIATE SCALING RELATIONS (2009, methodology): “(1) We also calculate the spectroscopic-like temperature, Tsl, as defined in Mazzotta et al. (2004), Tsl = ∫ n2T α−1/2dV ∫ n2T α−3/2dV → ∑N i ρiT α−1/2 i ∑N i ρiT α−3/2 i , (2) with α = 0.75.”
The structural and scaling properties of nearby galaxy clusters. II. The M-T relation (2005, methodology): “…if the difference is important at δ = 500: it is linked to differences between the temperature profile derived from projected Tsl(r) values and the true profile, which depends on the ICM structure along the line of sight (Mazzotta et al. 2004; Rasia et al. 2005), and thus a priori on radius.”
Lensing and x-ray mass estimates of clusters (simulations) (2012, methodology): “However, as demonstrated by Mazzotta et al. (2004) in their Fig.”
Total mass biases in X-ray galaxy clusters (2008, methodology): “By averaging over the whole sample we find the ratios: Tmw( r500) :Tsl( r500) :Tew( r500) = 1:1.13:1.27.”
Gas entropy in a representative sample of nearby X-ray galaxy clusters (REXCESS): relationship to gas mass fraction (2009, methodology): “This model was projected, taking into account the weighting scheme proposed by Vikhlinin (2006, see also Mazzotta et al. 2004) to correct for the bias introduce by fitting isothermal models to multi-temperature plasma emission, and fitted to the observed 2D annular temperature profile.”
X-RAY PROPERTIES OF THE FIRST SUNYAEV–ZEL'DOVICH EFFECT SELECTED GALAXY CLUSTER SAMPLE FROM THE SOUTH POLE TELESCOPE (2010, methodology): “To compute this expected ratio we have used the “spectroscopic-like” temperature (e.g., Mazzotta et al. 2004), given the density and temperature profiles used here.”
X-Ray and Sunyaev-Zel’dovich Effect Measurements of the Gas Mass Fraction in Galaxy Clusters (2006, background): “Second, cluster substructure can bias the average spectroscopic temperature of the cluster as a whole (e.g., Mathiesen & Evrard 2001; Mazzotta et al. 2004).”
Simulating the effect of active galactic nuclei feedback on the metal enrichment of galaxy clusters (2009, methodology): “As for the temperature, it is computed by following the prescription of spectroscopic like temper- ature introduced by Mazzotta et al. (2004).”
The universal galaxy cluster pressure profile from a representative sample of nearby systems (REXCESS) and the Y-SZ-M-500 relation (2009, unknown): “Although schemes to correct for this effect have been defined (Mazzotta et al. 2004; Vikhlinin 2006), it remains a potential source of systematics.”
Systematics in the X-ray cluster mass estimators (2006, methodology): “This temperature definition has been introduced in the analysis of the hydrodynamic simulations of galaxy clusters by Mazzotta et al. (2004) to provide a better approximation to the values extracted from fits of observed X-ray spectra (see also Vikhlinin 2006, for an extension to cooler systems…”
CHANDRA CLUSTER COSMOLOGY PROJECT. II. SAMPLES AND X-RAY DATA REDUCTION (2008, methodology): “In principle, this is not an exact method since this weighting function is proportional essentially to the emission measure integral, while the weighting corresponding to the spectroscopic mean is different (Mazzotta et al. 2004; Vikhlinin 2006).”
X-ray spectroscopy of galaxy clusters: studying astrophysical processes in the largest celestial laboratories (2009, background): “Mazzotta et al. (2004) derive a simple analytical approximat on to calculate the fitting result from a temperature mixture with an accuracy of a few percent for ICM temperatures above 3 keV.”
Chandra Temperature Profiles for a Sample of Nearby Relaxed Galaxy Clusters (2004, methodology): “…by the entropy-conserving versions of the smoothed particle dynamics (SPH) code (Springel & Hernquist 2002) used, e.g., by Ascasibar et al. and Borgani et al. A more detailed comparison with observations requires folding the simulation output through the detector response (Mazzotta et al. 2004).”
Formation of Galaxy Clusters (2012, methodology): “Furthermor , gas clumping also affects X– ray temperature which is measured by fitting the X–ray spectrum to a single–temperature plasma model (Mazzotta et al. 2004, Vikhlinin 2006).”
Scaling Properties of a Complete X-ray Selected Galaxy Group Sample (2014, methodology): “The results for the M-T and M-YX relations by Fabjan et al. (2011) were not used because of the known difference between the mass-weighted temperature used in their paper and the spectroscopic temperature (Mazzotta et al. 2004).”
Towards a realistic population of simulated galaxy groups and clusters (2013, background): “Previous studies (e.g. Mathiesen & Evrard 2001; Mazzotta et al. 2004; Rasia et al. 2006; Khedekar et al. 2013) found that the spectral temperatures are generally biased low compared to the mass-weighted temperatures.”