Detection of Dark Matter Skewness in the VIRMOS-DESCART Survey: Implications for Ω0

Weak gravitational lensing provides a direct statistical measure of dark matter distribution. The variance is easiest to measure, which constrains the degenerate product σ8Ω. The degeneracy is broken by measuring the skewness arising from the fact that densities must remain positive, which is not possible when the initially symmetric perturbations become nonlinear. Skewness measures the nonlinear mass scale, which in combination with the variance measures Ω0 directly. We present the first detection of dark matter skewness from the VIRMOS-DESCART survey. We have measured the full three-point function and its projections onto windowed skewness. We separate the lensing mode and the B-mode. The lensing skewness is detected for a compensated Gaussian on scales of 537 to be 3 = (1.06 ± 0.06) × 10-6. The B-modes are consistent with zero at this scale. The variance for the same window function is 2 = (5.32 ± 0.62 ± 0.98) × 10-5, resulting in S3 = 375. Comparing with N-body simulations, we find Ω0 < 0.5 at 90% confidence. The Canada-France-Hawaii Telescope legacy survey and newer simulations should be able to improve significantly on the constraint.

[1]  Y. Mellier,et al.  Gravity and Nongravity Modes in the VIRMOS-DESCART Weak-Lensing Survey , 2001, astro-ph/0109182.

[2]  T. Theuns,et al.  Discriminating Weak Lensing from Intrinsic Spin Correlations Using the Curl-Gradient Decomposition , 2000, astro-ph/0012336.

[3]  P. Hall,et al.  A Measurement of Weak Lensing by Large-Scale Structure in Red-Sequence Cluster Survey Fields , 2002, astro-ph/0202285.

[4]  Weak Lensing Results from the 75 Square Degree CTIO Survey , 2002, astro-ph/0210604.

[5]  U. Seljak,et al.  A Line of sight integration approach to cosmic microwave background anisotropies , 1996, astro-ph/9603033.

[6]  Y. Mellier,et al.  Source-lens clustering effects on the skewness of the lensing convergence , 2000, astro-ph/0012200.

[7]  Y. Mellier,et al.  Cosmic shear statistics and cosmology , 2001, astro-ph/0101511.

[8]  Matias Zaldarriaga,et al.  Higher Order Moments of the Cosmic Shear and Other Spin-2 Fields , 2003 .

[9]  N. Kaiser.  Clustering in real space and in redshift space , 1987 .

[10]  S. J. Dodds,et al.  Non-linear evolution of cosmological power spectra , 1996 .

[11]  Patterns in the weak shear 3-point correlation function , 2002, astro-ph/0201029.

[12]  Cosmic Shear and Power Spectrum Normalization with the Hubble Space Telescope , 2002, astro-ph/0203131.

[13]  Martin White,et al.  A New Algorithm for Computing Statistics of Weak Lensing by Large-Scale Structure , 1999 .

[14]  Masahiro Takada,et al.  The Three-Point Correlation Function for Spin-2 Fields , 2002, astro-ph/0210261.

[15]  Uros Seljak,et al.  Ray-tracing Simulations of Weak Lensing by Large-Scale Structure , 1999, astro-ph/9901191.

[16]  Detection of non-Gaussian signatures in the VIRMOS-DESCART lensing survey , 2002, astro-ph/0201032.

[17]  Normalizing the Temperature Function of Clusters of Galaxies , 1996, astro-ph/9610147.

[18]  Marc Davis,et al.  A survey of galaxy redshifts. V. The two-point position and velocity correlations. , 1983 .

[19]  The three-point correlation function of cosmic shear: I. The natural components , 2002, astro-ph/0207454.

[20]  Mining weak lensing surveys , 2002, astro-ph/0210478.

[21]  R W Hockney,et al.  Computer Simulation Using Particles , 1966 .

[22]  S. Dye,et al.  The shear power spectrum from the COMBO-17 survey , 2003 .

[23]  G. Bernstein,et al.  Weak-Lensing Results from the 75 Square Degree Cerro Tololo Inter-American Observatory Survey , 2003 .

[24]  Y. Mellier,et al.  Astronomy & Astrophysics manuscript no. (will be inserted by hand later) Likelihood Analysis of Cosmic Shear on Simulated and VIRMOS-DESCART Data ⋆ , 2002 .