The observed concentration–mass relation for galaxy clusters

By J. Comerford, P. Natarajan. 2007

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The properties of clusters of galaxies offer key insights into the assembly process of structure in the universe. Numerical simulations of cosmic structure formation in a hierarchical, dark matter dominated universe suggest that galaxy cluster concentrations, which are a measure of a halo's central density, decrease gradually with virial mass. However, cluster observations have yet to confirm this correlation. The slopes of the run of measured concentrations with virial mass are often either steeper or flatter than that predicted by simulations. In this work, we present the most complete sample of observed cluster concentrations and masses yet assembled, including new measurements for 10 strong-lensing clusters, thereby more than doubling the existing number of strong-lensing concentration estimates. We fit a power law to the observed concentrations as a function of virial mass, and find that the slope is consistent with the slopes found in simulations, though our normalization factor is higher. Observed lensing concentrations appear to be systematically larger than X-ray concentrations, a more pronounced effect than that found in simulations. We also find that at a fixed mass, the bulk of observed cluster concentrations are distributed lognormally, with the exception of a few anomalously high concentration clusters. We examine the physical processes likely responsible for the discrepancy between lensing and X-ray concentrations, and for the anomalously high concentrations in particular. The forthcoming Millennium simulation results will offer the most comprehensive comparison set to our findings of an observed concentration-mass power law relation.

Subfields: Astronomy and Astrophysics, Instrumentation, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/72306400717714d67cb173ac91119f60c0e118d1

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Citations in the corpus

Combined strong and weak lensing analysis of 28 clusters from the Sloan Giant Arcs Survey (2011, background): “…& Umetsu 2011; Morandi et al. 2011), although such high values of the concentration parameter appear to be common in the combined strong and weak lensing analysis of massive clusters (Comerford & Natarajan 2007; Broadhurst et al. 2008; Oguri et al. 2009; Umetsu et al. 2011b; Zitrin et al. 2011b).”
Concentration, spin and shape of dark matter haloes as a function of the cosmological model: WMAP1, WMAP3 and WMAP5 results (2008, background): “The concentrations of Comerford & Natarajan (2007) are a factor 1.6 higher than our WMAP1 results and a factor 2.0 higher than WMAP3 results, and selection effects would have to be rather severe to reconcile even our WMAP1 results with these observations.”
THE CLUSTER LENSING AND SUPERNOVA SURVEY WITH HUBBLE: AN OVERVIEW (2011, methodology): “Further discussion of some of the previous results from various methods are given in Comerford & Natarajan (2007); Coe (2010); Rines et al. (2010); King & Mead (2011).”
HUBBLE SPACE TELESCOPE COMBINED STRONG AND WEAK LENSING ANALYSIS OF THE CLASH SAMPLE: MASS AND MAGNIFICATION MODELS AND SYSTEMATIC UNCERTAINTIES (2014, background): “Although M0429 (z = 0.399) has been subject to various X-ray studies (Schmidt & Allen 2007; Comerford & Natarajan 2007; Maughan et al. 2008; Allen et al. 2008; Mann & Ebeling 2012), we did not find any previous SL, nor WL, analyses for this cluster outside the CLASH framework.”
SIMULATION OF THE COSMIC EVOLUTION OF ATOMIC AND MOLECULAR HYDROGEN IN GALAXIES (2009, methodology): “Here we shall use the result of Hennawi et al. (2007), chalo = 12.3 1 + z ( Mvir 1.3 · 1013 h−1M⊙ )−0.13 , (33) which is consistent with recent empirical values of the matter concentration in galaxy clusters derived from X-ray measurements and strong lensing data (Comerford & Natarajan 2007).”
Gravitational lensing (2010, background): “It is a puzzling and potentially highly important problem that strong-lensing analyses of galaxy clusters in many cases find that NFW density profiles well reproduce the observed image configurations, but with concentration parameters that are substantially larger than expected from numerical simula”
LoCuSS: Subaru Weak Lensing Study of 30 Galaxy Clusters (2009, result): “Our results are more significant than the earlier weak-lensing results (Comerford & Natarajan 2007; Mandelbaum et al. 2008).”
Formation of Galaxy Clusters (2012, result): “…2009; Sand et al. 2008, 2004; Tyson, Kochanski & dell’Antonio 1998), whereas concentrations are considerably higher than both theoretical predictions and most other observational determinations from X-ray and WL analyses (Comerford & Natarajan 2007, Oguri et al. 2012, 2009, Zitrin et al. 2011).”
Weighing simulated galaxy clusters using lensing and X-ray (2009, methodology): “…consists of measuring the concentration-mass relation of clusters and of comparing Article published by EDP Sciences Page 1 of 23 it with the theoretical predictions (e.g. Pointecouteau et al. 2005; Vikhlinin et al. 2005; Buote et al. 2007; Schmidt & Allen 2007; Comerford & Natarajan 2007).”
SEARCH FOR COSMIC-RAY-INDUCED GAMMA-RAY EMISSION IN GALAXY CLUSTERS (2013, methodology): “…by Chen et al. (2007).62 We solve for M200 using M200 = M200 × 200/500× [c200(M200)/c500(M200)]3 (Voit 2005), where the halo-mass-dependent concentration parameter c is derived from a power-law fit to a sample of observed galaxy cluster concentration and masses (Comerford & Natarajan 2007).”
DISSIPATION AND EXTRA LIGHT IN GALACTIC NUCLEI. IV. EVOLUTION IN THE SCALING RELATIONS OF SPHEROIDS (2008, unknown): “…1/(1+ z) is the halo concentration – althoughRvir is smaller for halos of a given mass at high redshift, they are less concentrated, yielding a weak size evolution similar to that observed (Bullock et al. 2001; Wechsler et al. 2002; Neto et al. 2007; Comerford & Natarajan 2007; Buote et al. 2007).”
DARK MATTER HALO PROFILES OF MASSIVE CLUSTERS: THEORY VERSUS OBSERVATIONS (2011, background): “The observational results span a variety of techniques, including strong and weak lensing (e.g., Comerford & Natarajan 2007; Broadhurst et al. 2008; Mandelbaum et al. 2008; Okabe et al. 2010; Oguri et al. 2011) X-ray observations of relaxed clusters (e.g., Buote et al. 2007; Vikhlinin et al. 2006;…”
New constraints on dark energy from the observed growth of the most X-ray luminous galaxy clusters (2007, background): “We have verified that including a log-normal scatter in concentration of ∼ 0.15 (e.g. Comerford & Natarajan 2007; Schmidt & Allen 2007) has no effect on our results.”
A Bayesian approach to strong lensing modelling of galaxy clusters (2007, methodology): “Comerford and Natarajan (2007) discuss the issues related to the determination of the concentration parameter with different techniques, and compare its measurement in a large compilation of galaxy clusters with the distribution of cvir in numerical simulations.”
CLASH: THE ENHANCED LENSING EFFICIENCY OF THE HIGHLY ELONGATED MERGING CLUSTER MACS J0416.1−2403 (2012, background): “The “over-concentration” problem in which lensing-selected clusters are found to have high concentrations (and large Einstein radii, e.g. Comerford & Natarajan 2007; Broadhurst et al. 2008; Broadhurst & Barkana 2008), is often attributed to a lensing selection bias towards higher concentrations of…”