Dark-matter halo profiles of a general cusp/core with analytic velocity and potential

Avishai Dekel, Guy Ishai, Aaron A. Dutton, Andrea Maccio

Research output: Contribution to journalArticle

Abstract

We present useful functions for the profiles of dark-matter (DM) haloes with a free inner slope, from cusps to cores, where the profiles of density, mass-velocity and potential are simple analytic expressions. Analytic velocity is obtained by expressing the mean density as a simple functional form, and deriving the local density by differentiation. The function involves four shape parameters, with only two or three free: a concentration parameter c, inner and outer asymptotic slopes α and γ, and a middle shape parameter ß. Analytic expressions for the potential and velocity dispersion exist for γ = 3 and for ß a natural number. We match the models to theDMhaloes in cosmological simulations, with and without baryons, ranging from steep cusps to flat cores. Excellent fits are obtained with three free parameters (c, α, γ) and ß = 2. For an analytic potential, similar fits are obtained for γ= 3 and ß = 2 with only two free parameters (c, α); this is our favourite model. A linear combination of two such profiles, with an additional free concentration parameter, provides excellent fits also for ß = 1, where the expressions are simpler. The fit quality is comparable to non-analytic popular models. An analytic potential is useful for modelling the inner-halo evolution due to gas inflows and outflows, studying environmental effects on the outer halo, and generating halo potentials or initial conditions for simulations. The analytic velocity can quantify simulated and observed rotation curves without numerical integrations.

Original languageEnglish (US)
Pages (from-to)1005-1022
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Volume468
Issue number1
DOIs
StatePublished - Jun 11 2017

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cusps
halos
dark matter
profiles
slopes
numerical integration
environmental effect
simulation
parameter
baryons
inflow
outflow
curves
gases
gas
modeling

Keywords

  • Dark matter
  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: haloes
  • Galaxies: structure

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Dark-matter halo profiles of a general cusp/core with analytic velocity and potential. / Dekel, Avishai; Ishai, Guy; Dutton, Aaron A.; Maccio, Andrea.

In: Monthly Notices of the Royal Astronomical Society, Vol. 468, No. 1, 11.06.2017, p. 1005-1022.

Research output: Contribution to journalArticle

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AB - We present useful functions for the profiles of dark-matter (DM) haloes with a free inner slope, from cusps to cores, where the profiles of density, mass-velocity and potential are simple analytic expressions. Analytic velocity is obtained by expressing the mean density as a simple functional form, and deriving the local density by differentiation. The function involves four shape parameters, with only two or three free: a concentration parameter c, inner and outer asymptotic slopes α and γ, and a middle shape parameter ß. Analytic expressions for the potential and velocity dispersion exist for γ = 3 and for ß a natural number. We match the models to theDMhaloes in cosmological simulations, with and without baryons, ranging from steep cusps to flat cores. Excellent fits are obtained with three free parameters (c, α, γ) and ß = 2. For an analytic potential, similar fits are obtained for γ= 3 and ß = 2 with only two free parameters (c, α); this is our favourite model. A linear combination of two such profiles, with an additional free concentration parameter, provides excellent fits also for ß = 1, where the expressions are simpler. The fit quality is comparable to non-analytic popular models. An analytic potential is useful for modelling the inner-halo evolution due to gas inflows and outflows, studying environmental effects on the outer halo, and generating halo potentials or initial conditions for simulations. The analytic velocity can quantify simulated and observed rotation curves without numerical integrations.

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