Abstract
We constrain cosmological parameters and galaxy-bias parameters using the
combination of galaxy clustering and galaxy-galaxy lensing measurements from
the Dark Energy Survey Year-3 data. We describe our modeling framework and
choice of scales analyzed, validating their robustness to theoretical
uncertainties in small-scale clustering by analyzing simulated data. Using a
linear galaxy bias model and redMaGiC galaxy sample, we obtain constraints on
the matter content of the universe to be $Ømega_m =
0.325^+0.033_-0.034$. We also implement a non-linear galaxy bias model to
probe smaller scales that includes parameterizations based on hybrid
perturbation theory, and find that it leads to a 17% gain in cosmological
constraining power. Using the redMaGiC galaxy sample as foreground lens
galaxies, we find the galaxy clustering and galaxy-galaxy lensing measurements
to exhibit significant signals akin to decorrelation between galaxies and mass
on large scales, which is not expected in any current models. This likely
systematic measurement error biases our constraints on galaxy bias and the
$S_8$ parameter. We find that a scale-, redshift- and sky-area-independent
phenomenological decorrelation parameter can effectively capture this
inconsistency between the galaxy clustering and galaxy-galaxy lensing. We
perform robustness tests of our methodology pipeline and demonstrate stability
of the constraints to changes in the theory model. After accounting for this
decorrelation, we infer the constraints on the mean host halo mass of the
redMaGiC galaxies from the large-scale bias constraints, finding the galaxies
occupy halos of mass approximately $1.5 10^13 M_ødot/h$.
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