Flat-cored Dark Matter in Cuspy Clusters of Galaxies

By A. El-Zant, Y. Hoffman, Joel R. Primack, F. Combes, I. Shlosman. 2003

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Sand and coworkers have measured the central density profile of cluster MS 2137-23 with gravitational lensing and velocity dispersion and removed the stellar contribution with a reasonable M/L. The resulting dark matter (DM) distribution within r < 50 h-1 kpc was fitted by a density cusp of r-β with β = 0.35, in an apparent contradiction to the cold dark matter prediction of β ~ 1. The disagreement worsens if adiabatic compression of the DM by the infalling baryons is considered. Following El-Zant, Shlosman, & Hoffman, we argue that dynamical friction acting on galaxies moving within the DM background counters the effect of adiabatic compression by transfering their orbital energy to the DM, thus heating up and softening the cusp. Using N-body simulations we show that indeed the inner DM distribution flattens (with β ≈ 0.35 for a cluster like MS 2137-23) when the galaxies spiral inward. We find as a robust result that while the DM distribution becomes core-like, the overall mass distribution preserves its cuspy nature, in agreement with X-ray and lensing observations of clusters.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/5e59061afc9c6625371f293a40b25960127df93d

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Citations in the corpus

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): “Dynamical friction acting on orbiting galaxies can pump energy into the diffuse DM component and flatten the inner density slope (El-Zant et al. 2004), and this flattening can be interpretedas a decrease in concentration (Ricotti et al. 2007).”
THE DENSITY PROFILES OF MASSIVE, RELAXED GALAXY CLUSTERS. II. SEPARATING LUMINOUS AND DARK MATTER IN CLUSTER CORES (2012, background): “…have indeed shown that dynamical friction between infalling satellites and the DM halo can heat the cusp and reduce the central DM density (e.g., El-Zant et al. 2001, 2004; Nipoti et al. 2004; Jardel 11 In any case, the highly uncertain contribution from subhalos may dominate this signal (e.g.,…”
Small scale problems of the $\Lambda$CDM model: a short review (2016, background): “While the flattening provided by the DFBC (see Figure 6), starts at higher redshifts (z 5), at z ' 3 the DM density profile, in the pure SNFF scenario, the flattening remains similar to the NFW profile [298,300,326].”
Dark halo response and the stellar initial mass function in early-type and late-type galaxies (2010, background): “…Gnedin & Zhao 2002; Read & Gilmore 2005; Governato et al. 2010); dynamical friction operating on baryonic clumps (El-Zant, Shlosman & Hoffman 2001; El-Zant et al. 2004; Elmegreen et al. 2008; Jardel & Sellwood 2009) or galactic bars (Weinberg & Katz 2002; HolleyBockelmann et al. 2005; Sellwood…”
Impact of baryon physics on dark matter structures: a detailed simulation study of halo density profiles (2010, methodology): “The erasure of the central DM cusp in galaxies by infalling satellites was proposed by El-Zant et al. (2001) and for the case of clusters by El-Zant et al. (2004).”
Selection bias in dynamically measured supermassive black hole samples: its consequences and the quest for the most fundamental relation (2016, background): “…processes such as dynamical friction and AGN feedback effects may contribute to the creationof cores in the inner regions of massive galaxies (e.g., El-Zant et al. 2004; Tonini et al. 2006; Martizzi et al. 2013; El-Zant et al.2016). c© 2016 RAS, MNRAS000, 1– 20 A number of observations and black…”
THE DENSITY PROFILES OF MASSIVE, RELAXED GALAXY CLUSTERS. I. THE TOTAL DENSITY OVER THREE DECADES IN RADIUS (2012, background): “These include heating of the central cusp via dynamical friction with infalling satellites (e.g., El-Zant et al. 2001, 2004; Nipoti et al. 2004; RomanoDı́az et al. 2008; Jardel & Sellwood 2009; Johansson et al. 2009; Del Popolo 2012), feedback from supernovae in lowmass galaxies (Governato et al.…”
Cuspy No More: How Outflows Affect the Central Dark Matter and Baryon Distribution in Lambda CDM Galaxies (2012, background): “…(Navarro et al. 1996a; Dekel et al. 2003b,a; Mo & Mao 2004; Read & Gilmore 2005; Mashchenko et al. 2006; Goerdt et al. 2006; Tonini et al. 2006; El-Zant et al. 2004; Romano-Dı́az et al. 2009; Del Popolo 2009; Lackner & Ostriker 2010; Goerdt et al. 2010; de Souza et al. 2011; Pontzen &…”