The effect of non-Gaussianity on error predictions for the Epoch of Reionization (EoR) 21-cm power spectrum
Sep 15, 20144 pages
Published in:
- Mon.Not.Roy.Astron.Soc. 449 (2015) 1, L41-L45
- Published: May 1, 2015
e-Print:
- 1409.4420 [astro-ph.CO]
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Abstract: (Oxford University Press)
The Epoch of Reionization (EoR) 21-cm signal is expected to become increasingly non-Gaussian as reionization proceeds. We have used seminumerical simulations to study how this affects the error predictions for the EoR 21-cm power spectrum. We expect for a Gaussian random field where N_k is the number of Fourier modes in each k bin. We find that non-Gaussianity is important at high SNR where it imposes an upper limit [SNR]_l. For a fixed volume V, it is not possible to achieve SNR > [SNR]_l even if N_k is increased. The value of [SNR]_l falls as reionization proceeds, dropping from ∼500 at to ∼10 at for a [150.08 Mpc]^3 simulation. We show that it is possible to interpret [SNR]_l in terms of the trispectrum, and we expect if the volume is increased. For SNR ≪ [SNR]_l we find with A ∼ 0.95–1.75, roughly consistent with the Gaussian prediction. We present a fitting formula for the SNR as a function of N_k, with two parameters A and [SNR]_l that have to be determined using simulations. Our results are relevant for predicting the sensitivity of different instruments to measure the EoR 21-cm power spectrum, which till date have been largely based on the Gaussian assumption.Note:
- Accepted for publication in MNRAS Letters. The definitive version is available at http://mnrasl.oxfordjournals.org/content/449/1/L41
- methods: statistical
- cosmology: theory
- dark ages, reionization, first stars
- diffuse radiation
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