Guoliang Li Guoliang Li Shanghai Astronomic Shanghai Astronomic Observatory Observatory November 1st, 2006 November 1st, 2006 The giant arc statistic in the three-year WMAP cosmological model COLLABORATORS: Shude mao (JBO) Yipeng Jing, Xi Kang, Weipeng Lin (SHAO) Matthias Bartelmann, Massimo Menegentti (Heidelberg) Liang Gao (Durham)
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The g iant a rc statistic in the three-year WMAP cosmological model
The g iant a rc statistic in the three-year WMAP cosmological model. Guoliang Li. Shanghai Astronomic Observatory. November 1st , 2006. COLLABORATORS: Shude mao (JBO) Yipeng Jing, Xi Kang, Weipeng Lin (SHAO) Matthias Bartelmann, Massimo Menegentti (Heidelberg) Liang Gao (Durham). - PowerPoint PPT Presentation
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– Sources have 0.5, 1, 1.5 arcsecond effective diameter
– Ellipticity: 1-b/a, from 0.5 to 1
• Integrate the cross-sections of all clusters to get the total lensing cross sections.
Optical depth as a function of source redshift
• Optical depth ~ 10-7 for zs=1, but 10-6 for zs=4
– Several previous values are too high due to incorrect assumptions of sigma_8 and L/W definition
– Consistent with Dalal et al. (2004)
Strong zs dependence
Weaker dependence on ellipticity and source size
Optical depth as a function of lens redshift
• For sources at high z, probe clusters at high redshift• Gladders et al. who found all of their lensing clusters
were at z>0.62; understood if source z is high.
• Comparing with Bartelmann (1998), Dalal et al. (2004) pointed that the numbers of lens and should be increased by a factor of 2. The giant arcs number which they predicted is in good agreement with almost all of the observations.
• What will happen in the three-year WMAP universe?
Giant arcs in the WMAP3 cosmology
• The WMAP three-year model has lower m and 8 compared with the WMAP one-year model.
• The lower m (0.238) and 8 (0.74) both reduce the number of giants
• We compared the arc predictions in the usual LCDM and WMAP three-year model:– Using two 300/h Mpc N-body simulations– The predicted number is reduced by a factor of
about six in the WMAP three year model– Easily understood due to the abundance of
clusters
Predicted number of giant arcs
• Effect of star formation? Likely a factor of 2• Source redshift distribution, size, ellipticity(modest)
The way to increase the lensing efficiency
• The asysmetric of lens----------------ok
• The merger effect------------------- --ok
• The substructure-----------------------ok
• The redshift distribution of source ---ok
• The size and shape of source ---modest
• The mass around the line of sight----<7%
• The baryon effect ---not very clear(~2)
Summary
• Optical depth may be too low in the WMAP three-year model (with 8=0.74)
• We need many larger giant arc unbiased samples -- they will come as by-products of weak lensing surveys.