## Weak gravitational lensing effects on the determination of and from SNeIa
In this article we present an analytical calculation of the
probability distribution of the magnification of distant sources due
to weak gravitational lensing from non-linear scales. We use a
realistic description of the non-linear density field, which has
already been compared with numerical simulations of structure
formation within hierarchical scenarios. Then, we can directly express
the probability distribution of the
magnification in terms of the probability distribution of the density
contrast realized on non-linear scales (typical of galaxies) where the
local slope of the initial linear power-spectrum is
. We recover the behaviour seen by
numerical simulations: peaks at a
value slightly smaller than the mean
and it shows an extended large Then, we study the effects of weak lensing on the derivation of the cosmological parameters from SNeIa. We show that the inaccuracy introduced by weak lensing is not negligible: for two observations at and . However, observations can unambiguously discriminate between and . Moreover, in the case of a low-density universe one can clearly distinguish an open model from a flat cosmology (besides, the error decreases as the number of observ ed SNeIa increases). Since distant sources are more likely to be "demagnified" the most probable value of the observed density parameter is slightly smaller than its actual value. On the other hand, one may obtain some valuable information on the properties of the underlying non-linear density field from the measure of weak lensing distortions.
This article contains no SIMBAD objects. ## Contents- 1. Introduction
- 2. Density contrast probability distribution
- 3. Magnification by weak lensing
- 3.1. Definition
- 3.2. Probability distribution
- 3.3. Scaling functions and
- 4. Dependence on cosmology and redshift
- 5. Galactic halos
- 6. Derivation of cosmological parameters
- 7. Bias
- 8. Conclusion
- Acknowledgements
- References
© European Southern Observatory (ESO) 2000 Online publication: February 25, 2000 |