Cosmological Parameter Survey Using the Gravitational Lensing Method

Premana W Premadi , Hugo Martel , Richard Matzner , Toshifumi Futamase, PASA, 18 (2), in press.
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Summary

We summarize the results as follows: (1) The cosmological distances play a critical role in nearly every aspect of gravitational lensing, both weak and strong. Consequently, the properties of gravitational lenses depend much more strongly upon $\lambda _0$ than any other cosmological parameters. (2) Magnification and shear are examples of weak lensing caused primarily by the distribution of background matter, with negligible contribution from galaxies. Consequently, these effects are sensitive to the value of $\sigma _8$. (3) Multiple images are examples of strong lensing, caused mainly by galaxies. Consequently, the properties of multiple images are independent of $\sigma _8$. They are determined by the cosmological distances, which depend primarily upon $\lambda _0$, and by the details of the galactic models, which are usually independent of the cosmological parameters. Therefore, observations of weak lensing can be used to determine the cosmological constant and the unbiased density structure of the universe, while observations of strong lensing can be used to determine the cosmological constant and the internal structure of galaxies and clusters. (4) The dependences upon H0 and $\Omega _0$ are not as simple, because varying these parameters affects gravitational lensing in several ways that often partly cancel one another. Determining $\lambda _0$ and $\sigma _8$ from observations seems much more promising than determining $\Omega _0$ and H0. The complete results of this survey are described in greater detail in Premadi et al (2001).

Figure 5: Histograms of the distribution of image separations in arc seconds, for various models. Top two rows: models with $\Omega _0=0.2$, $\lambda _0=0.8$; bottom two rows: models with $\Omega _0=1$, $\lambda _0=0$. The values of H0 (in units of

$\rm km\,s^{-1}Mpc^{-1}$), $\sigma _8$, and the number of double images are indicated.
\begin{figure} \par\psfig{file=figure5.ps,height=15cm,angle=90}\par\end{figure}

Next Section: References
Title/Abstract Page: Cosmological Parameter Survey Using
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Contents Page: Volume 18, Number 2

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