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arXiv · 0812.5083

Catastrophic Photo-z Errors and the Dark Energy Parameter Estimates with Cosmic Shear

L. Sun·Z. -H. Fan·C. Tao·J. -P. Kneib·S. Jouvel·A. Tilquin
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Abstract

We study the impact of catastrophic errors occurring in the photometric redshifts of galaxies on cosmological parameter estimates with cosmic shear tomography. We consider a fiducial survey with 9-filter set and perform photo-z measurement simulations. It is found that a fraction of 1% galaxies at z_{spec}~0.4 is misidentified to be at z_{phot}~3.5. We then employ both chi^2 fitting method and the extension of Fisher matrix formalism to evaluate the bias on the equation of state parameters of dark energy, w_0 and w_a, induced by those catastrophic outliers. By comparing the results from both methods, we verify that the estimation of w_0 and w_a from the fiducial 5-bin tomographic analyses can be significantly biased. To minimize the impact of this bias, two strategies can be followed: (A) the cosmic shear analysis is restricted to 0.5 320 and 860 respectively in order to reduce the joint bias in (w_0,w_a) to be smaller than 2σand 1σ. This spectroscopic survey (option B) will improve the Figure of Merit of option A by a factor \times 1.5 thus making such a survey strongly desirable.

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L. Sun, Z. -H. Fan, C. Tao, J. -P. Kneib, S. Jouvel, A. Tilquin. 2009-04-28. Catastrophic Photo-z Errors and the Dark Energy Parameter Estimates with Cosmic Shear. https://doi.org/10.1088/0004-637x%2F699%2F2%2F958

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