Intrinsic alignment boosting: Direct measurement of intrinsic alignments in cosmic shear data

Details Intrinsic alignment boosting: Direct measurement of intrinsic alignments in cosmic shear data Intrinsic alignment boosting: Direct measurement of intrinsic alignments in cosmic shear data

2010-03-22

arxiv.org/abs/1003.4211v2

Astronomy and Astrophysics, Volume 517, 2010, id. A4

Astronomy and Astrophysics

Astrophysics

Cosmology and Extragalactic Astrophysics

15 pages, 7 figures; minor changes to match accepted version; published in Astronomy and Astrophysics

Scientific paper

10.1051/0004-6361/201014482

Intrinsic alignments constitute the major astrophysical systematic for cosmological weak lensing surveys. We present a purely geometrical method with which one can study gravitational shear-intrinsic ellipticity correlations directly in weak lensing data. Linear combinations of second-order cosmic shear measures are constructed such that the intrinsic alignment signal is boosted while suppressing the contribution by gravitational lensing. We then assess the performance of a specific parametrisation of the weights entering these linear combinations for three representative survey models. Moreover a relation between this boosting technique and the intrinsic alignment removal via nulling is derived. For future all-sky weak lensing surveys with photometric redshift information the boosting technique yields statistical errors on model parameters of intrinsic alignments whose order of magnitude is compatible with current constraints determined from indirect measurements. Parameter biases due to a residual cosmic shear signal are negligible in case of quasi-spectroscopic redshifts and remain sub-dominant for typical values of the photometric redshift scatter. We find good agreement between the performance of the intrinsic alignment removal based on the boosting technique and standard nulling methods, possibly indicating a fundamental limit in the separation of lensing and intrinsic alignment signals.

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