Speaker
Description
We constrain cosmological parameters Ωm and σ8 from a joint analysis of galaxy clustering and galaxy-galaxy lensing from DESI Legacy Imaging Surveys Data Release 9 (DR9), covering approximately 10000 square degrees and spanning the redshift range of 0.1 to 0.9. In order to study the cosmological parameters dependence on redshift, we divide the galaxies into seven volume-limited lens samples, each with an equal width in photometric redshift. To retrieve the intrinsic projected correlation function wp(rp), we employ a novel method to account for redshift uncertainties. Additionally, we measure the galaxy-galaxy weak lensing signal ∆Σ(rp) for each lens sample, using source galaxies selected from the shear catalog by applying our Fourier Quad pipeline to DR9 images. We model these observables within the flat ΛCDM framework, employing the minimal bias model. To ensure the reliability of the minimal bias model, we apply conservative scale cuts: rp > 8 and 12 h−1Mpc, for wp(rp) and ∆Σ(rp), respectively. With an abundance of lens and source galaxies, our constraints on the derived parameter S 8 ≡ σ8√Ωm/0.3 at low redshift achieve a comparable level of tightness as those obtained from Planck CMB or 3×2pt analysis. Our findings suggest a mild tendency that S8 increases with lens redshift, although this trend is only marginally significant. When we combine non-overlapping samples, the value of S 8 is determined to be 0.85 ± 0.02, consistent with the results from Planck but higher than the 3×2pt analysis at approximately a 2σ level. Although several improvements in measurements and modeling could enhance the accuracy of our final constraints, the general agreement with canonical values demonstrates the potential of our work for future precise and accurate cosmology.
