Mark C. Neyrinck, Lin Forrest Yang
We present an experiment in which we 'ring' a set of cosmological N-body-simulation initial conditions, placing spikes in its initial power spectrum at different wavenumber bins. We then measure where these spikes end up in the final conditions. In the usual, overdensity power spectrum, most sensitive to contracting and collapsing dense regions, initial power on slightly non-linear scales (k ~ 0.3 h/Mpc) smears to smaller scales, coming to dominate the initial power once there. In log-density and Gaussianized-density power spectra, the sensitivity to low-density (expanding) as well as high-density regions produces a different response: initial spikes spread symmetrically in scale, both upward and downward. We also test the difference between a crude approximation of the Ly-{\alpha} flux field, and its Gaussianized form. In the power spectrum of the reciprocal density, 1/(1 + {\delta}), spikes migrate to larger scales, indicating the magnifying effect voids have on small-scale modes. We give a toy model that qualitatively explains the symmetric power spreading in Gaussianized-density power spectra. Also, we discuss how to use this framework to estimate power-spectrum covariance matrices. This can be used to track the fate of information in the Universe, that takes the form of initial degrees of freedom, one random spike per initial mode.
View original:
http://arxiv.org/abs/1305.1629
No comments:
Post a Comment