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Impact of a Warm Dark Matter late-time velocity dispersion on large-scale structures
Cosmology and Nongalactic Astrophysics · Submitted 4 Jun 2012
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim We find that the late-time velocity dispersion has a negligible effect on the power spectrum on perturbative scales and on the halo mass function.
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The abstract, sentence by sentence
We investigate whether the late-time (at $z\leq 100$) velocity dispersion expected in Warm Dark Matter scenarios could have some effect on the cosmic web (i.e., outside of virialized halos). We consider effective hydrodynamical equations, with a pressurelike term that agrees at the linear level with the analysis of the Vlasov equation. Then, using analytical methods, based on perturbative expansions and the spherical dynamics, we investigate the impact of this term for a 1 keV dark matter particle. We find that the late-time velocity dispersion has a negligible effect on the power spectrum on perturbative scales and on the halo mass function. However, it has a significant impact on the probability distribution function of the density contrast at $z \sim 3$ on scales smaller than $0.1 h^{-1}$Mpc, which correspond to Lyman-$\alpha$ clouds. Finally, we note that numerical simulations should start at $z_i\geq 100$ rather than $z_i \leq 50$ to avoid underestimating gravitational clustering at low redshifts.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We investigate whether the late-time (at $z\leq 100$) velocity dispersion expected in Warm Dark Matter scenarios could have some effect on the cosmic web (i.e., outside of virialized halos). | contribution 0.92 | 0.45 | 0.04 | hedged possibility 0.96 |
| s1 | We consider effective hydrodynamical equations, with a pressurelike term that agrees at the linear level with the analysis of the Vlasov equation. | method 0.99 | 0.72 | 0.02 | asserted 0.96 |
| s2 | Then, using analytical methods, based on perturbative expansions and the spherical dynamics, we investigate the impact of this term for a 1 keV dark matter particle. | method 0.99 | 0.90 | 0.02 | asserted 0.71 |
| s3 | We find that the late-time velocity dispersion has a negligible effect on the power spectrum on perturbative scales and on the halo mass function. | result 1.00 | 0.96 | 0.49 | asserted 1.00 |
| s4 | However, it has a significant impact on the probability distribution function of the density contrast at $z \sim 3$ on scales smaller than $0.1 h^{-1}$Mpc, which correspond to Lyman-$\alpha$ clouds. | result 1.00 | 0.93 | 0.30 | asserted 1.00 |
| s5 | Finally, we note that numerical simulations should start at $z_i\geq 100$ rather than $z_i \leq 50$ to avoid underestimating gravitational clustering at low redshifts. | future work 0.96 | 0.38 | 0.07 | asserted 0.89 |
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The paper
Original abstract
We investigate whether the late-time (at $z\leq 100$) velocity dispersion expected in Warm Dark Matter scenarios could have some effect on the cosmic web (i.e., outside of virialized halos). We consider effective hydrodynamical equations, with a pressurelike term that agrees at the linear level with the analysis of the Vlasov equation. Then, using analytical methods, based on perturbative expansions and the spherical dynamics, we investigate the impact of this term for a 1 keV dark matter particle. We find that the late-time velocity dispersion has a negligible effect on the power spectrum on perturbative scales and on the halo mass function. However, it has a significant impact on the probability distribution function of the density contrast at $z \sim 3$ on scales smaller than $0.1 h^{-1}$Mpc, which correspond to Lyman-$\alpha$ clouds. Finally, we note that numerical simulations should start at $z_i\geq 100$ rather than $z_i \leq 50$ to avoid underestimating gravitational clustering at low redshifts.
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What this paper does with the arXiv papers it cites
What it cites · 29 sentences without a confident label
Uses the method or tool of 2 papers
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As in [ref] , we use a steepest-descent approach to obtain $(δ_x)$ from the spherical dynamics [ref] .
Dynamics of gravitational clustering II. Steepest-descent method for the quasi-linear regime · Probability distribution of the density contrast · 1.00
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Following [ref] , we write the linear density power spectrum today in terms of the reference CDM power spectrum as P_L,WDM(k,z=0) = P_L,CDM(k,z=0) T(k)^2 ,
Constraining Warm Dark Matter candidates including sterile neutrinos and light gravitinos with WMAP and the Lyman-alpha forest · Setup · 0.80
Cites as support 2 papers
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We also find that the late-time velocity dispersion has a negligible impact on the halo mass function at $z ≤5$ (in any case, below the $10%$ accuracy that can be guaranteed by simulations), although at very low mass and high redshift, the cutoff may become sharper [ref] .
Constraints on Warm Dark Matter from Cosmological Reionization · Conclusion · 0.97
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Thus, CDM simulations typically predict too many satellite galaxies around Milky-Way-sized central galaxies as compared with observations [ref] .
Dark Matter Substructure in Galactic Halos · Introduction · 0.96
Cites as background 11 papers
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As is well known, the WDM scenario leads to a much smaller halo mass function at low masses than in the CDM case, because of the lack of power on small scales [ref] .
Halo Formation in Warm Dark Matter Models · Halo mass function · 0.85
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Most works focus on the decrease of the flux power spectrum due to the high-$k$ damping of the WDM power spectrum set by the relativistic free streaming [ref] .
Can sterile neutrinos be the dark matter? · Probability distribution of the density contrast · 0.88
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Most works focus on the decrease of the flux power spectrum due to the high-$k$ damping of the WDM power spectrum set by the relativistic free streaming [ref] .
Constraining Warm Dark Matter candidates including sterile neutrinos and light gravitinos with WMAP and the Lyman-alpha forest · Probability distribution of the density contrast · 0.88
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