The Nature of Dark Matter and the Density Profile and Central Behavior of Relaxed Halos

Salvador-Solé, E.; Manrique, Alberto; González-Casado, Guillermo; Hansen, Steen H.

doi:10.1086/520325

Cited by 42 publications

(58 citation statements)

References 42 publications

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“…This characteristic corroborates the expectations from our model and is consistent with earlier results of Zhao et al (2003). Salvador-Solé et al (2007) also predict a theoretical mass-concentration relation through their theoretical density profile which relates to the accretion rate of halos. The free parameter of their model is then fit to the mass-concentration relation of Zhao et al (2003).…”

Section: Discussionsupporting

confidence: 93%

Concentration, ellipsoidal collapse, and the densest dark matter haloes

Okoli¹,

Afshordi²

2015

Mon. Not. R. Astron. Soc.

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The smallest dark matter haloes are the first objects to form in the hierarchical structure formation of cold dark matter (CDM) cosmology and are expected to be the densest and most fundamental building blocks of CDM structures in our universe. Nevertheless, the physical characteristics of these haloes have stayed illusive, as they remain well beyond the current resolution of N-body simulations (at redshift zero). However, they dominate the predictions (and uncertainty) in expected dark matter annihilation signal, amongst other astrophysical observables. Using the conservation of total energy and the ellipsoidal collapse framework, we can analytically find the mean and scatter of concentration c and 1-D velocity dispersion σ 1d for haloes of different virial mass M 200 . Both c and σ 1d /M 1/3 200 are in good agreement with numerical results within the regime probed by simulations -slowly decreasing functions of mass that approach constant values at large masses. In particular, the predictions for the 1-D velocity dispersion of cluster mass haloes are surprisingly robust as the inverse heat capacity of cosmological haloes crosses zero at M 200 ∼ 10 14 M . However, we find that current extrapolations from simulations to smallest CDM haloes dramatically depend on the assumed profile (e.g. NFW vs. Einasto) and fitting function, which is why theoretical considerations, such as the one presented here, can significantly constrain the range of feasible predictions.

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Section: Discussionsupporting

confidence: 93%

Concentration, ellipsoidal collapse, and the densest dark matter haloes

Okoli¹,

Afshordi²

2015

Mon. Not. R. Astron. Soc.

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“…Cole & Lacey 1996). However, a number of analytical studies have claimed that the density profile should depend on spectral index (e.g., Hoffman & Shaham 1985;Syer & White 1998;Subramanian et al 2000;Huffenberger & Seljak 2003;Salvador-Solé et al 2007), and these have been supported by numerical simulations providing similar evidence (e.g., Crone et al 1994;Eke et al 2001;Ricotti 2003;Cen et al 2004;Reed et al 2005;Ricotti et al 2007).…”

Section: Introductionmentioning

confidence: 92%

“…merging, smooth accretion) that drive this form (cf., Lu et al 2006;Salvador-Solé et al 2007), but a theoretical understanding of the origin of the mass profile is essential. Is the form of the profile set by non-linear processes during the virialisation of the halo, or is there an imprint of the primordial power spectrum P (k)?…”

Section: Introductionmentioning

confidence: 99%

Dark Matter Halo Profiles in Scale-Free Cosmologies

Knollmann

Power

Knebe

2008

Dark Matter in Astroparticle and Particle Physics

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We explore the dependence of the central logarithmic slope of dark matter halo density profiles α on the spectral index n of the linear matter power spectrum P (k) using cosmological N -body simulations of scale-free models (i.e. P (k) ∝ k n ). These simulations are based on a set of clear, reproducible and physically motivated criteria that fix the appropriate starting and stopping times for runs, and allow one to compare haloes across models with different spectral indices and mass resolutions. For each of our simulations we identify samples of well resolved haloes in dynamical equilibrium and we analyse their mass profiles. By parameterising the mass profile using a "generalised" Navarro, Frenk & White profile in which the central logarithmic slope α is allowed to vary while preserving the r −3 asymptotic form at large radii, we obtain preferred central slopes for haloes in each of our models. There is a strong correlation between α and n, such that α becomes shallower as n becomes steeper. However, if we normalise our mass profiles by r −2 , the radius at which the logarithmic slope of the density profile is −2, we find that these differences are no longer present. This is apparent if we plot the maximum slope γ = 3(1 − ρ/ρ) as a function of r/r −2 -we find that the profiles are similar for haloes forming in different n models. This reflects the importance of concentration, and reveals that the concentrations of haloes forming in steep-n cosmologies tend to be smaller than those of haloes forming in shallow-n cosmologies. We conclude that there is no evidence for convergence to a unique central asymptotic slope, at least on the scales that we can resolve.

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“…First, the halo growth has been recognized (see Zhao et al 2003;Wechsler et al 2006;Hoffman et al 2007;Diemand et al 2007) to comprise two stages: an early fast collapse including a few violent major mergers, that builds up the halo main "body" with the structure set by dynamical relaxation; and a later, quasi-equilibrium stage when the body is nearly unaffected, while the outskirts develop from the inside-out by minor mergers and smooth accretion (see Salvador-Solé et al 2007). The transition is provided by the time when a DM gravitational potential attains its maximal depth; i.e., the radial peak of the circular velocity v 2 c ≡ GM/R attains its maximal height, along a given growth history (see Li et al 2007).…”

Section: Two-stage Evolutionmentioning

confidence: 99%

Gamma rays from annihilations at the galactic center in a physical dark matter distribution

Lapi

Paggi²,

Cavaliere³

et al. 2010

A&A

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We discuss the γ-ray signal to be expected from dark matter (DM) annihilations at the Galactic center. We describe the DM distribution in the Galactic halo, based on the Jeans equation for self-gravitating, anisotropic equilibria. In solving the Jeans equation, we adopted the specific correlation between the density ρ(r) and the velocity dispersion σ 2 r (r) expressed by the powerlaw behavior of the DM "entropy" K ≡ σ 2 r /ρ 2/3 ∝ r α with α ≈ 1.25−1.3. Indicated (among others) by several recent N-body simulations, this correlation is privileged by the form of the radial pressure term in the Jeans equation, and it yields a main-body profile consistent with the classic self-similar development of DM halos. In addition, we required the Jeans solutions to satisfy regular boundary conditions both at the center (finite pressure, round gravitational potential) and on the outskirts (finite overall mass). With these building blocks, we derived physical solutions, dubbed "α-profiles". We find the one with α = 1.25, suitable for the Galaxy halo, to be intrinsically flatter at the center than the empirical NFW formula, yet steeper than the empirical Einasto profile. On scales of 10 −1 deg it yields annihilation fluxes lower by a factor 5 than the former, yet higher by a factor 10 than the latter. Such fluxes will eventually fall within the reach of the Fermi satellite. We show the effectiveness of the α-profile in relieving the astrophysical uncertainties related to the macroscopic DM distribution, and discuss its expected performance as a tool instrumental in interpreting the upcoming γ-ray data in terms of DM annihilation.

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The Nature of Dark Matter and the Density Profile and Central Behavior of Relaxed Halos

Cited by 42 publications

References 42 publications

Concentration, ellipsoidal collapse, and the densest dark matter haloes

Concentration, ellipsoidal collapse, and the densest dark matter haloes

Dark Matter Halo Profiles in Scale-Free Cosmologies

Gamma rays from annihilations at the galactic center in a physical dark matter distribution

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