Dark Halos: The Flattening of the Density Cusp by Dynamical Friction

By A. El-Zant, I. Shlosman, Y. Hoffman. 2001

324 citations recorded by the source corpus.

N-body simulations and analytical calculations of the gravitational collapse in an expanding universe predict that halos should form with a diverging inner density profile, the cusp. There are some observational indications that the dark matter distribution in galaxies might be characterized by a finite core. This "core catastrophe" has prompted a search for alternatives to the cold dark matter (CDM) cosmogony. It is shown here that the discrepancy between theory and observations can be very naturally resolved within the standard CDM model, provided that gas is not initially smoothly distributed in the dark matter halo but rather is concentrated in clumps of mass ≥0.01% of the total mass of the system. Dynamical friction acting on these lumps moving in the background of the dark matter particles dissipates the clumps' orbital energy and deposits it in the dark matter. Using Monte Carlo simulations, it is shown that the dynamical friction provides a strong enough drag and that with realistic baryonic mass fractions, the available orbital energy of the clumps is sufficient to heat the halo and turn the primordial cusp into a finite, nondiverging core—overcoming the competing effect of adiabatic contraction due to the gravitational influence of the shrinking baryonic component. Depending on the initial conditions, the total density distribution may become either more or less centrally concentrated. Possible consequences of the proposed mechanism for other problems in the CDM model and for the formation and early evolution of the baryonic component of galaxies are also briefly discussed.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/5b97fa64e4b0ff8a04be8c3cc904f96657ddfc36

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Citations in the corpus

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).”
Cusp-core transformations in dwarf galaxies: observational predictions (2012, background): “…we have a very clumpy structure in the ISM and in the stellar distribution, it does not trigger the formation of a dark matter core in our case; the mechanism proposed by Mashchenko et al. (2006) (see also El-Zant et al. 2001) does not work here, probably because our clumps are not massive enough.”
Dark matter cores all the way down (2015, background): “4 An alternative mechanism that may act in tandem with collisionless heating from supernovae is angular momentum transfer from dense infalling lumps (El-Zant et al. 2001; Goerdt et al. 2010; Cole et al. 2011; Nipoti & Binney 2015).”
The DiskMass Survey VII. The distribution of luminous and dark matter in spiral galaxies (2013, background): “However, several processes may occur that could also expand the halo, such as dynamical friction between the halo and infalling galaxies (e.g., El-Zant et al. 2001), or mass outflows from central starbursts and active galactic nuclei (Read & Gilmore 2005; Governato et al. 2012; Pontzen & Governato…”
Bar-driven Dark Halo Evolution: A Resolution of the Cusp-Core Controversy (2001, background): “Even so, both Binney et al. (2001) and El-Zant et al. (2001) discuss mechanisms by which the baryonic component might produce a core.”
The dependence of dark matter profiles on the stellar-to-halo mass ratio: a prediction for cusps versus cores (2013, background): “Two main mechanisms have been shown to cause expansion: supernova feedback (Navarro et al. 1996; Mo & Mao 2004; Read & Gilmore 2005; Mashchenko et al. 2006; Pontzen & Governato 2012) and dynamical friction (El-Zant et al. 2001; Tonini et al. 2006; Romano-Dı́az et al. 2008; Goerdt etal.”
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].”
Multi-frequency analysis of neutralino dark matter annihilations in the Coma cluster (2005, background): “According to a recent model (El-Zant et al. 2001), baryons might sink in the central part of DM halos after getting clumped into dense gas clouds, with the halo density profile in the final configuration found to be described by a profile (labeled here as B profile) with a large core radius (see,…”
THE COUPLING BETWEEN THE CORE/CUSP AND MISSING SATELLITE PROBLEMS (2012, background): “…02138 5 Sternberg Astronomical Institute, Moscow State University, Universitetskiy pr. 13, 119992 Moscow, Russia or the orbital decay of compact baryonic objects (El-Zant et al. 2001; Goerdt et al. 2010; Cole et al. 2011) can under plausible conditions flatten the central cusps of CDM-like haloes.”
The Dramatic Size Evolution of Elliptical Galaxies and the Quasar Feedback (2008, background): “The numerical simulations by El-Zant et al. (2001) showed that dynamical friction between baryon and DM clouds within the scale radius of the Navarro et al. (1997) density distribution (r ≤ rs) is strong enough to overcome the expected adiabatic contraction of DM caused by the deepening of the…”
Numerical simulations of the dark universe: State of the art and the next decade (2012, background): “of dense stellar clumps against the smooth background DM halo [366, 373, 386, 387], and repeated and violent oscillations in the central potential due to energy injection from active galactic nuclei [388] or supernova-driven galactic outflows [389–392].”
A METHOD FOR MEASURING (SLOPES OF) THE MASS PROFILES OF DWARF SPHEROIDAL GALAXIES (2011, background): “…of Cambridge, Madingley Road, Cambridge CB30HA 3 Hubble Fellow volving baryons might alter the original structure of a dark matter halo (e.g., Blumenthal et al. 1986; Navarro et al. 1996; El-Zant et al. 2001; Gnedin et al. 2004; Tonini et al. 2006; Governato et al. 2010; Pontzen & Governato 2011).”
The impact of baryonic physics on the structure of dark matter haloes: the view from the FIRE cosmological simulations (2015, background): “On the other hand, core formation via enhanced dynamical friction from the dense infalling sub-structure (e.g. El-Zant et al. 2001) is unlikely to play a significant role for the halo mass range probed here, because feedback lowers the density of infalling sub-halos relative to their DM-only…”
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.…”