Alas, the dark matter structures were not that trivial

Kasper B. Schmidt, Steen H. Hansen, Andrea Maccio

Research output: Contribution to journalArticle

Abstract

The radial density profile of dark matter structures has been observed to have an almost universal behavior in numerical simulations; however, the physical reason for this behavior remains unclear. It has previously been shown that if the pseudo phase-space density, ρ/σ⊙ de, is a beautifully simple power law in radius, with the "golden values" ∋ p 3 and d p r (i.e., the phase-space density is only dependent on the radial component of the velocity dispersion), then one can analytically derive the radial variation of the mass profile, dispersion profile, etc. That would imply, if correct, that we just have to explain why ρ/σr 3-rα and then we would understand everything about equilibrated DM structures. Here we use a set of simulated galaxies and clusters of galaxies to demonstrate that there are no such golden values, but that each structure instead has its own set of values. Considering the same structure at different redshifts shows no evolution of the phase-space parameters toward fixed points. There is also no clear connection between the halo virialized mass and these parameters. This implies that we still do not understand the origin of the profiles of dark matter structures.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume689
Issue number1 PART 2
DOIs
StatePublished - Jan 1 2008

Fingerprint

dark matter
space density
profiles
galaxies
power law
halos
radii
simulation
parameter

Keywords

  • Dark matter
  • Galaxies: Halos
  • Methods: Data analysis
  • Methods: Numerical

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Alas, the dark matter structures were not that trivial. / Schmidt, Kasper B.; Hansen, Steen H.; Maccio, Andrea.

In: Astrophysical Journal, Vol. 689, No. 1 PART 2, 01.01.2008.

Research output: Contribution to journalArticle

Schmidt, Kasper B. ; Hansen, Steen H. ; Maccio, Andrea. / Alas, the dark matter structures were not that trivial. In: Astrophysical Journal. 2008 ; Vol. 689, No. 1 PART 2.
@article{31765acfa6714dc59e0bf3aed9727764,
title = "Alas, the dark matter structures were not that trivial",
abstract = "The radial density profile of dark matter structures has been observed to have an almost universal behavior in numerical simulations; however, the physical reason for this behavior remains unclear. It has previously been shown that if the pseudo phase-space density, ρ/σ⊙ de, is a beautifully simple power law in radius, with the {"}golden values{"} ∋ p 3 and d p r (i.e., the phase-space density is only dependent on the radial component of the velocity dispersion), then one can analytically derive the radial variation of the mass profile, dispersion profile, etc. That would imply, if correct, that we just have to explain why ρ/σr 3-rα and then we would understand everything about equilibrated DM structures. Here we use a set of simulated galaxies and clusters of galaxies to demonstrate that there are no such golden values, but that each structure instead has its own set of values. Considering the same structure at different redshifts shows no evolution of the phase-space parameters toward fixed points. There is also no clear connection between the halo virialized mass and these parameters. This implies that we still do not understand the origin of the profiles of dark matter structures.",
keywords = "Dark matter, Galaxies: Halos, Methods: Data analysis, Methods: Numerical",
author = "Schmidt, {Kasper B.} and Hansen, {Steen H.} and Andrea Maccio",
year = "2008",
month = "1",
day = "1",
doi = "10.1086/595783",
language = "English (US)",
volume = "689",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1 PART 2",

}

TY - JOUR

T1 - Alas, the dark matter structures were not that trivial

AU - Schmidt, Kasper B.

AU - Hansen, Steen H.

AU - Maccio, Andrea

PY - 2008/1/1

Y1 - 2008/1/1

N2 - The radial density profile of dark matter structures has been observed to have an almost universal behavior in numerical simulations; however, the physical reason for this behavior remains unclear. It has previously been shown that if the pseudo phase-space density, ρ/σ⊙ de, is a beautifully simple power law in radius, with the "golden values" ∋ p 3 and d p r (i.e., the phase-space density is only dependent on the radial component of the velocity dispersion), then one can analytically derive the radial variation of the mass profile, dispersion profile, etc. That would imply, if correct, that we just have to explain why ρ/σr 3-rα and then we would understand everything about equilibrated DM structures. Here we use a set of simulated galaxies and clusters of galaxies to demonstrate that there are no such golden values, but that each structure instead has its own set of values. Considering the same structure at different redshifts shows no evolution of the phase-space parameters toward fixed points. There is also no clear connection between the halo virialized mass and these parameters. This implies that we still do not understand the origin of the profiles of dark matter structures.

AB - The radial density profile of dark matter structures has been observed to have an almost universal behavior in numerical simulations; however, the physical reason for this behavior remains unclear. It has previously been shown that if the pseudo phase-space density, ρ/σ⊙ de, is a beautifully simple power law in radius, with the "golden values" ∋ p 3 and d p r (i.e., the phase-space density is only dependent on the radial component of the velocity dispersion), then one can analytically derive the radial variation of the mass profile, dispersion profile, etc. That would imply, if correct, that we just have to explain why ρ/σr 3-rα and then we would understand everything about equilibrated DM structures. Here we use a set of simulated galaxies and clusters of galaxies to demonstrate that there are no such golden values, but that each structure instead has its own set of values. Considering the same structure at different redshifts shows no evolution of the phase-space parameters toward fixed points. There is also no clear connection between the halo virialized mass and these parameters. This implies that we still do not understand the origin of the profiles of dark matter structures.

KW - Dark matter

KW - Galaxies: Halos

KW - Methods: Data analysis

KW - Methods: Numerical

UR - http://www.scopus.com/inward/record.url?scp=58449110804&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=58449110804&partnerID=8YFLogxK

U2 - 10.1086/595783

DO - 10.1086/595783

M3 - Article

VL - 689

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1 PART 2

ER -