0035-8711
The cosmological impact of intrinsic alignment model choice for cosmic shear
Kirk
Donnacha
UCL, Dept Phys & Astron, London WC1E 6BT, England
Rassat
Anais
Observ Sauverny, Swiss Fed Inst Technol Lausanne EPFL, LASTRO, CH-1290 Versoix, Switzerland
Host
Ole
UCL, Dept Phys & Astron, London WC1E 6BT, England
Bridle
Sarah
UCL, Dept Phys & Astron, London WC1E 6BT, England
2012
We consider the effect of galaxy intrinsic alignments (IAs) on dark energy constraints from weak gravitational lensing. We summarize the latest version of the linear alignment model of IAs, following a brief note of Hirata & Seljak and further interpretation by Laszlo et al. We show the cosmological bias on the dark energy equation of state parameters w0 and wa$ that would occur if IAs were ignored. We find that w0 and wa are both catastrophically biased, by an absolute value of just greater than unity under the Fisher matrix approximation. This contrasts with a bias several times larger for the earlier IA implementation. Therefore, there is no doubt that IAs must be taken into account for future stage III experiments and beyond. We use a flexible grid of IA and galaxy bias parameters as used in previous work and investigate what would happen if the Universe is described by used the latest IA model, but we assumed the earlier version. We find that despite the large difference between the two IA models, the grid flexibility is sufficient to remove cosmological bias and recover the correct dark energy equation of state. In an appendix, we compare observed shear power spectra to those from a popular previous implementation and explain the differences.
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