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Analytic model for the matter power spectrum, its covariance matrix and baryonic effects


Mohammed, Irshad; Seljak, Uroš (2014). Analytic model for the matter power spectrum, its covariance matrix and baryonic effects. Monthly Notices of the Royal Astronomical Society, 445(4):3382-3400.

Abstract

We develop a model for the matter power spectrum as the sum of Zeldovich approximation and even powers of k, i.e. A0−A2k2+A4k4−..., compensated at low k. With terms up to k4, the model can predict the true power spectrum to a few per cent accuracy up to k ∼ 0.7 h Mpc−1, over a wide range of redshifts and models. The An coefficients contain information about cosmology, in particular amplitude of fluctuations. We write a simple form of the covariance matrix as a sum of Gaussian part and A0 variance, which reproduces the simulations remarkably well. In contrast, we show that one needs an N-body simulation volume of more than 1000 (Gpc h−1)3 to converge to 1 per cent accuracy on covariance matrix. We investigate the supersample variance effect and show it can be modelled as an additional parameter that can be determined from the data. This allows a determination of σ8 amplitude to about 0.2 per cent for a survey volume of 1(Gpc h−1)3, compared to 0.4 per cent otherwise. We explore the sensitivity of these coefficients to baryonic effects using hydrodynamic simulations of van Daalen et al. We find that because of baryons redistributing matter inside haloes all the coefficients A2n for n > 0 are strongly affected by baryonic effects, while A0 remains almost unchanged, a consequence of halo mass conservation. Our results suggest that observations such as weak lensing power spectrum can be effectively marginalized over the baryonic effects, while still preserving the bulk of the cosmological information contained in A0 and Zeldovich terms

Abstract

We develop a model for the matter power spectrum as the sum of Zeldovich approximation and even powers of k, i.e. A0−A2k2+A4k4−..., compensated at low k. With terms up to k4, the model can predict the true power spectrum to a few per cent accuracy up to k ∼ 0.7 h Mpc−1, over a wide range of redshifts and models. The An coefficients contain information about cosmology, in particular amplitude of fluctuations. We write a simple form of the covariance matrix as a sum of Gaussian part and A0 variance, which reproduces the simulations remarkably well. In contrast, we show that one needs an N-body simulation volume of more than 1000 (Gpc h−1)3 to converge to 1 per cent accuracy on covariance matrix. We investigate the supersample variance effect and show it can be modelled as an additional parameter that can be determined from the data. This allows a determination of σ8 amplitude to about 0.2 per cent for a survey volume of 1(Gpc h−1)3, compared to 0.4 per cent otherwise. We explore the sensitivity of these coefficients to baryonic effects using hydrodynamic simulations of van Daalen et al. We find that because of baryons redistributing matter inside haloes all the coefficients A2n for n > 0 are strongly affected by baryonic effects, while A0 remains almost unchanged, a consequence of halo mass conservation. Our results suggest that observations such as weak lensing power spectrum can be effectively marginalized over the baryonic effects, while still preserving the bulk of the cosmological information contained in A0 and Zeldovich terms

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Item Type:Journal Article, refereed, original work
Communities & Collections:National licences > 142-005
Dewey Decimal Classification:530 Physics
Uncontrolled Keywords:neutrinos, methods: analytical, galaxies: haloes, galaxies: statistics, cosmological parameters, large scale structures of Universe
Language:English
Date:21 December 2014
Deposited On:31 Oct 2018 17:29
Last Modified:24 Sep 2019 23:41
Publisher:Oxford University Press
ISSN:0035-8711
OA Status:Green
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1093/mnras/stu1972
Related URLs:https://www.swissbib.ch/Search/Results?lookfor=nationallicenceoxford101093mnrasstu1972 (Library Catalogue)

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