Testing phenomenological and theoretical models of dark matter density profiles with galaxy clusters

Silva, Leandro Beraldo e; Lima, M.; Sodré, L.

doi:10.1093/mnras/stt1761

Cited by 27 publications

(35 citation statements)

References 53 publications

(70 reference statements)

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“…In particular, we concentrate our attention on the neighborhood of E = Φ(0), that is to the center of the system, where we perform an accurate asymptotic analysis. In this respect, our findings do not hinder the fitting of DARKexp predictions to observations and N −body simulations, which is reported to be quite good [20,[25][26][27]. Indeed, no cusp/core ambiguity may arise when the DARKexp n(E) is directly compared to the differential energy distribution extracted from N −body simulations [20,27], while the direct comparison of the DARKexp mass density, numerically computed as in [19], to that of astrophysical objects [25,26] and of N −body simulations [27] are restricted to distances too large to distinguish a cusp from a small core.…”

supporting

confidence: 64%

Cored density profiles in the DARKexp model

Destri

2018

J. Cosmol. Astropart. Phys.

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The DARKexp model represents a novel and promising attempt to solve a long standing problem of statistical mechanics, that of explaining from first principles the quasistationary states at the end of the collisionless gravitational collapse. The model, which yields good fits to observation and simulation data on several scales, was originally conceived to provide a theoretical basis for the 1/r cusp of the Navarro-Frenk-White profile. In this note we show that it also allows for cored density profiles that, when viewed in three dimensions, in the r → 0 limit have the conical shape characteristic of the Burkert profile. It remains to be established whether both cusps and cores, or only one of the two types, are allowed beyond the asymptotic analysis of this work.

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supporting

confidence: 64%

Cored density profiles in the DARKexp model

Destri

2018

J. Cosmol. Astropart. Phys.

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“…For example, the resulting density profile can be fit to gravitational lensing data from galaxy clusters, as done for other models in [11]. Another direct test can be made with data from rotation curves of spiral galaxies.…”

Section: Discussionmentioning

confidence: 99%

Statistical mechanics of self-gravitating systems: Mixing as a criterion for indistinguishability

et al. 2014

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We propose an association between the phase-space mixing level of a self-gravitating system and the indistinguishability of its constituents (stars or dark matter particles). This represents a refinement in the study of systems exhibiting incomplete violent relaxation. Within a combinatorial analysis similar to that of Lynden-Bell, we make use of this association to obtain a distribution function that deviates from the Maxwell-Boltzmann distribution, increasing its slope for high energies. Considering the smallness of the occupation numbers for large distances from the center of the system, we apply a correction to Stirling's approximation which increases the distribution slope also for low energies. The distribution function thus obtained presents some resemblance to the "S" shape of distributions associated with cuspy density profiles (as compared to the distribution function obtained from the Einasto profile), although it is not quite able to produce sharp cusps. We also argue how the association between mixing level and indistinguishability can provide a physical meaning to the assumption of particle-permutation symmetry in the N-particle distribution function, when it is used to derive the one-particle Vlasov equation, which raises doubts about the validity of this equation during violent relaxation.

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“…The correlation function ξ hm (r) is, in fact, an average of the observed overdensity around halos of similar masses, ρ h,obs (r) , since ξ hm (r) = ρ h,obs (r) /ρ m − 1. In the context of the halo model, the average observed overdensity is given by the sum of two contributions [33,[37][38][39],…”

Section: Halo Modelmentioning

confidence: 99%

Relation between the turnaround radius and virial mass in f(R) model

Lopes¹,

Voivodic²,

Abramo³

et al. 2019

J. Cosmol. Astropart. Phys.

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We investigate the relationship between the turnaround radius R t and the virial mass M v of cosmic structures in the context of ΛCDM model and in an f (R) model of modified gravity -namely, the Hu-Sawicki model. The turnaround radius is the distance from the center of the cosmic structure to the shell that is detaching from the Hubble flow at a given time, while the virial mass is defined, for this work, as the mass enclosed within the volume where the density is 200 times the background density. We employ a new approach by considering that, on average, gravitationally bound astrophysical systems (e.g., galaxies, groups and clusters of galaxies) follow, in their innermost region, a Navarro-Frenk-White density profile, while beyond the virial radius (R v ) the profile is well approximated by the 2-halo term of the matter correlation function. By combining these two properties together with the information drawn from solving the spherical collapse for the structures, we are able to connect two observables that can be readily measured in cosmic structures: the turnaround radius and the virial mass. In particular, we show that, in ΛCDM, the turnaround mass at z = 0 is related to the virial mass of that same structure by M t 3.07 M v , while in terms of the radii we have that R t 3.7 R v (for virial masses of 10 13 h −1 M ). In the f (R) model, on the other hand, we have M t 3.43 M v and R t 4.1 R v , for |f R0 | = 10 −6 and the same mass scale. Therefore, the difference between ΛCDM and f (R) in terms of these observable relations is of order ∼ 10−20% even for a relatively mild strength of the modification of gravity (|f R0 | = 10 −6 ). For the turnaround radius itself we find a difference of ∼ 9% between the weakly modification in gravity considered in this work (|f R0 | = 10 −6 ) and ΛCDM for a mass of 10 13 h −1 M . Once observations allow precisions of this order or better in measurements of the turnaround R t , as well as the virial mass M v (and/or the virial radius R v ), these quantities will become powerful tests of modified gravity.

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Testing phenomenological and theoretical models of dark matter density profiles with galaxy clusters

Cited by 27 publications

References 53 publications

Cored density profiles in the DARKexp model

Cored density profiles in the DARKexp model

Statistical mechanics of self-gravitating systems: Mixing as a criterion for indistinguishability

Relation between the turnaround radius and virial mass in f(R) model

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