Speaker
Description
Recently, several studies reported a significant discrepancy between
the clustering and lensing of the Baryon Oscillation Spectroscopic
Survey (BOSS) galaxies in the Planck cosmology. We construct a
simple yet powerful model based on the linear theory to assess whether
this discrepancy points toward deviations from Planck. Focusing
on scales $10{<}R{<}30\,h^{-1}\mathrm{Mpc}$, we model the amplitudes of
clustering and lensing of BOSS LOWZ galaxies using three parameters:
galaxy bias $b_\mathrm{g}$, galaxy-matter cross-correlation coefficient
$r_\mathrm{gm}$, and $A$, defined as the ratio between the true and
Planck values of $\sigma_8$. Using the cross-correlation matrix
as a diagnostic, we detect systematic uncertainties that drive spurious
correlations among the low-mass galaxies. After building a clean LOWZ
sample with $r_\mathrm{gm}{\sim}1$, we derive a joint constraint of
$b_\mathrm{g}$ and $A$ from clustering+lensing, yielding
$b_\mathrm{g}{=}2.47_{-0.30}^{+0.36}$ and $A{=}0.81_{-0.09}^{+0.10}$,
i.e., a $2\sigma$ tension with Planck. However, due to the strong
degeneracy between $b_\mathrm{g}$ and $A$, systematic uncertainties in
$b_\mathrm{g}$ could masquerade as a tension with $A{=}1$. To ascertain
this possibility, we develop a new method to measure $b_\mathrm{g}$
from the cluster-galaxy cross-correlation and cluster weak lensing
using an overlapping cluster sample. By applying the independent bias
measurement ($b_\mathrm{g}{=}1.76{\pm}0.22$) as a prior, we
successfully break the degeneracy and derive stringent constraints of
$b_\mathrm{g}{=}2.02_{-0.15}^{+0.16}$ and $A{=}0.96{\pm}{0.07}$.
Therefore, our result suggests that the large-scale clustering and
lensing of LOWZ galaxies are consistent with Planck, while the
different bias estimates may be related to some observational
systematics that needs to be mitigated in future surveys.
