AAS 205th Meeting, 9-13 January 2005
Session 131 The Deep Dark Universe
Oral, Wednesday, January 12, 2005, 2:00-3:30pm, Royal Palm 4-6

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[131.02] Safety in numbers: Gravitational Lensing Degradation of the Luminosity Distance-Redshift Relation

E. V. Linder (Berkeley Lab), D. E. Holz (University of Chicago and LANL)

For exploring dark energy, the cosmic expansion history, and the distance scale, standardizable candles such as Type Ia supernovae remain one of the most promising and robust tools. As such observations are pushed to higher redshifts, the observed flux is increasingly affected by gravitational lensing magnification due to intervening structure along the line-of-sight. We simulate and analyze the non-Gaussian probability distribution function of de/amplification due to lensing of standard candles, quantify the effect of a convolution over many independent sources (which acts to restore the intrinsic average (unlensed) luminosity due to flux conservation), and compute the additional uncertainty due to lensing on derived cosmological parameters. For example, the ``degradation factor'' due to lensing is a one-third reduction in the effective number of usable supernovae at z=1.5 (for sources with intrinsic flux dispersion of 10%). We also present a useful expression for the effective increased dispersion in standard candles due to lensing, as a function of redshift.

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.