On the spin parameter of dark-matter haloes
The study by White on the growth of angular momentum in dark haloes is extended towards a more detailed investigation of the spin parameter $$\lambda\equiv L\sqrt{E}/GM^{2.5}$$. Starting from the Zel'dovich approximation to structure formation, a dark halo is approximated by a homogeneous ellip...
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| Hauptverfasser: | , |
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| Dokumenttyp: | Article (Journal) |
| Sprache: | Englisch |
| Veröffentlicht: |
01 February 1995
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| In: |
Monthly notices of the Royal Astronomical Society
Year: 1995, Jahrgang: 272, Heft: 3, Pages: 570-578 |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/272.3.570 |
| Online-Zugang: | Verlag, kostenfrei, Volltext: http://dx.doi.org/10.1093/mnras/272.3.570
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| Verfasserangaben: | Matthias Steinmetz and Matthias Bartelmann |
| Zusammenfassung: | The study by White on the growth of angular momentum in dark haloes is extended towards a more detailed investigation of the spin parameter $$\lambda\equiv L\sqrt{E}/GM^{2.5}$$. Starting from the Zel'dovich approximation to structure formation, a dark halo is approximated by a homogeneous ellipsoid with the inertial tensor of the (highly irregular) Lagrangian region $$\Upsilon$$ from which the dark halo forms. Within this approximation, an expression for the spin parameter can be derived, which depends on the geometry of $$\Upsilon$$,the cosmological density parameter Ω0, the overdensity of the dark halo, and the tidal torque exerted on it. For Gaussian random fields, this expression can be evaluated statistically. As a result,we derive a probability distribution of the spin parameter which gives $$\lambda\simeq0.07_{-0.05}^{+0.04}$$, consistent with numerical investigations. This probability distribution steeply rises with increasing spin parameter, reaching its maximum at $$\lambda\simeq0.025$$. The 10 (50, 90) percentile values are λ = 0.02 (0.05, 0.11, respectively). There is a weak anticorrelation of the spin parameter with the peak height ν of the density fluctuation field, $$\lambda\propto v^{-0.29}$$. The dependence on Ω0 and the variance σ of the density-contrast field is very weak; there is only a marginal tendency for the spin parameter to be slightly larger for late-forming objects in an open universe. Due to the weak dependence on σ, our results should be quite generally applicable and independent of the special type of the fluctuation spectrum. |
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| Beschreibung: | Gesehen am 29.09.2017 |
| Beschreibung: | Online Resource |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/272.3.570 |