TITLE:
Spectroscopic source redshifts and parameter constraints from weak lensing and CMB
AUTHOR(S):
Mustapha Ishak and Christopher M. Hirata (Princeton University)
DATE:
2004 May 03 (arXiv, v1, posted); 2004 May 24 (Phys. Rev. Lett., submitted);
2004 Oct 27 (revised); 2004 Oct 27 (transferred to Phys. Rev. D); 2005 Jan 03 (Phys. Rev. D, accepted);
2005 Jan 03 (arXiv, v2, posted); 2005 Jan 24 (Phys. Rev. D, published).
AVAILABILITY:
arXiv astro-ph/0405042 (free).
PUBLICATION INFORMATION: Physical Review D, 71, 023002 (2005), 8 pages.
ABSTRACT:
Weak lensing is a potentially robust and model-independent cosmological probe, but its accuracy is dependent on knowledge of the
redshift distribution of the source galaxies used. The most robust way to determine the redshift distribution is via spectroscopy of a
subsample of the source galaxies. We forecast constraints from combining CMB anisotropies with cosmic shear using a spectroscopically
determined redshift distribution, varying the number of spectra Nspec obtained from 64 to infinity. The source redshift
distribution is expanded in a Fourier series, and the amplitudes of each mode are considered as parameters to be constrained via both
the spectroscopic and weak lensing data. We assume independent source redshifts, and consider in what circumstances this is a good
approximation (the sources are clustered and for narrow spectroscopic surveys with many objects this results in the redshifts being
correlated). It is found that for the surveys considered and for a prior of 0.04 on the calibration parameters, the addition of
redshift information make significant improvements on the constraints on the cosmological parameters; however, beyond
Nspec ~ few x 103 the addition of further spectra will make only a very small improvement to the cosmological
parameters. We find that a better calibration makes large Nspec more useful. Using an eigenvector analysis, we find that
the improvement continues with even higher Nspec, but not in directions that dominate the uncertainties on the standard
cosmological parameters.
ADS BIBLIOGRAPHIC CODE: 2005PhRvD..71b3002I
COMMENTS: