Day 1280

Thursday.


1706.09195
Generating log-normal mock catalog of galaxies in redshift space
Agrawal, et al

Present a public code to generate a mock galaxy catalog in redshift space assuming a log-normal probability density function of galaxy and matter density fields.  Draw galaxies by Poisson-sampling the log-normal field, and calculate the velocity field from the linearized continuity equation of matter fields, assuming zero vorticity.  This procedure yields a PDF of the pairwise velocity fields that is quantitatively similar to that of N-body sims.  Check fidelity of the catalog, showing that the measured 2pt correlation function and power spectrum in real space agree with the input precisely.  Find that a linear bias relation in the power spectrum does not guarantee a linear bias relation in the density contrasts, leading to a cross-correlation coefficient of matter and galaxies devoting from unity on small scales.  Also find that linearizing the Jacobian of the real-to-redshift space mapping provides a poor model for the 2pt statistics in z space.  That is, non-linear redshift-space distortion is dominated by non-linearity in the Jacobian.  The power spectrum in z space shows a damping on small scales that is qualitatively similar to that of the well-known FoG effect due to random velocities, except that the log-normal mock does not include random velocities.  This damping is a consequence of NL in the Jacobian, and thus attributing the damping of the PS solely to FoG, as commonly done in the literature is misleading.


1706.09359
Dark energy survey year 1 results: multi-probe methodology and simulated likelihood analyses
Krause, Eifler, Zuntz, et al

Present the methodology for and detail the implementation of the DES 3x2pt DES Y1 analysis, which combines configuration-space 2pt statistics from 3 different cosmological probes: cosmic shear, gg lensing, and galaxy clustering, using data from the first year of DES observations.  Developed 2 independent modeling pipelines and describe the code validation process.  Derive expressions for analytical real-space multi-probe covariances, and describe their validation with numerical sims.  Stress-test the inference pipelines in simulated likelihood analyses that vary 6-7 cosmology parameters plus 20 nuisance parameters and precisely resemble the analysis to be presented in the DES 3x2pt analysis paper, using a variety of simulated input data vectors with varying assumptions.  Find that any disagreement between pipelines leads to changes in assigned likelihood Delta chi2 <= 0.045 with respect to the statistical error of the DES Y1 data vector.  Also find that angular binning and survey do not impact the analytic covariance at a significant level.  Determine lower bounds on scales used for analysis of galaxy clustering (8 Mpc/h) and gg lensing (12 Mpc/h) such that their impact of modeling uncertainties in the non-linear regime is well below statistical errors, and show that the analysis choices are robust against a variety of systematics.  These tests demonstrate that the analysis pipeline is robust, which yields unbiased cosmological parameter inferences for the flagship 3x2pt DES Y1 analysis.  Emphasize that the level of independent code development and subsequent code comparison as demonstrated in this paper is necessary to produce credible constraints from increasingly complex multi-probe analyses of current data.