Observational Evidence for Weak Gravitational Lensing by Large Scale Structure
Villumsen, Jens Verner
Original · EN
A single very deep 10' field has been imaged to r 26. There are 2682 galaxies with 23 ≤ r ≤ 26 with a size significantly larger than the seeing disk in the field. After correcting for telescope aberrations, possible guiding errors, and signal degradation due to seeing, I find a polarization signal of amplitude |p|=2.7%, with an uncertainty of 1.2% (95% confidence limit). For the 1773 galaxies with 23 ≤ r ≤ 25, the measured amplitude is 2.4% ± 1.2% (95% confidence limit). If this observed polarization is due to gravitational lensing by large scale structure, cosmological inferences can be made. The polarization amplitude would indicate that Ω₀ × σ₈ ≈ 1. The amplitude probability distribution is a Rayleigh distribution with variance σₚ² so the probability P(1/2 < |p|/σₚ <2) = 75%, and P(1/3 < |p|/σₚ < 3) = 93.5%. The measurement of the polarization amplitude in a single field can be used to constrain cosmological models since σₚ ∝ Ω₀ × σ₈.
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