TY - JOUR

T1 - Cosmological systematics beyond nuisance parameters: form-filling functions

AU - Kitching, T. D.

AU - Amara, A.

AU - Abdalla, F. B.

AU - Joachimi, B.

AU - Refregier, A.

AU - Kitching, Thomas

PY - 2009/11/1

Y1 - 2009/11/1

N2 - In the absence of any compelling physical model, cosmological
systematics are often misrepresented as statistical effects and the
approach of marginalizing over extra nuisance systematic parameters is
used to gauge the effect of the systematic. In this article, we argue
that such an approach is risky at best since the key choice of function
can have a large effect on the resultant cosmological errors.
As an alternative we present a functional form-filling technique in
which an unknown, residual, systematic is treated as such. Since the
underlying function is unknown, we evaluate the effect of every
functional form allowed by the information available (either a hard
boundary or some data). Using a simple toy model, we introduce the
formalism of functional form filling. We show that parameter errors can
be dramatically affected by the choice of function in the case of
marginalizing over a systematic, but that in contrast the functional
form-filling approach is independent of the choice of basis set.
We then apply the technique to cosmic shear shape measurement
systematics and show that a shear calibration bias of |m(z)|

AB - In the absence of any compelling physical model, cosmological
systematics are often misrepresented as statistical effects and the
approach of marginalizing over extra nuisance systematic parameters is
used to gauge the effect of the systematic. In this article, we argue
that such an approach is risky at best since the key choice of function
can have a large effect on the resultant cosmological errors.
As an alternative we present a functional form-filling technique in
which an unknown, residual, systematic is treated as such. Since the
underlying function is unknown, we evaluate the effect of every
functional form allowed by the information available (either a hard
boundary or some data). Using a simple toy model, we introduce the
formalism of functional form filling. We show that parameter errors can
be dramatically affected by the choice of function in the case of
marginalizing over a systematic, but that in contrast the functional
form-filling approach is independent of the choice of basis set.
We then apply the technique to cosmic shear shape measurement
systematics and show that a shear calibration bias of |m(z)|

UR - http://www.scopus.com/inward/record.url?scp=70350754519&partnerID=8YFLogxK

U2 - 10.1111/j.1365-2966.2009.15408.x

DO - 10.1111/j.1365-2966.2009.15408.x

M3 - Article

VL - 399

SP - 2107

EP - 2128

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

ER -