KiDS-450 + 2dFLenS: Cosmological parameter constraints from weak
  gravitational lensing tomography and overlapping redshift-space galaxy
  clustering
  We perform a combined analysis of cosmic shear tomography, galaxy-galaxy
lensing tomography, and redshift-space multipole power spectra (monopole and
quadrupole) using 450 deg$^2$ of imaging data by the Kilo Degree Survey (KiDS)
overlapping with two spectroscopic surveys: the 2-degree Field Lensing Survey
(2dFLenS) and the Baryon Oscillation Spectroscopic Survey (BOSS). We restrict
the galaxy-galaxy lensing and multipole power spectrum measurements to the
overlapping regions with KiDS, and self-consistently compute the full
covariance between the different observables using a large suite of $N$-body
simulations. We methodically analyze different combinations of the observables,
finding that galaxy-galaxy lensing measurements are particularly useful in
improving the constraint on the intrinsic alignment amplitude (by 30%, positive
at $3.5\sigma$ in the fiducial data analysis), while the multipole power
spectra are useful in tightening the constraints along the lensing degeneracy
direction (e.g. factor of two stronger matter density constraint in the
fiducial analysis). The fully combined constraint on $S_8 \equiv \sigma_8
\sqrt{\Omega_{\rm m}/0.3} = 0.742 \pm 0.035$, which is an improvement by 20%
compared to KiDS alone, corresponds to a $2.6\sigma$ discordance with Planck,
and is not significantly affected by fitting to a more conservative set of
scales. Given the tightening of the parameter space, we are unable to resolve
the discordance with an extended cosmology that is simultaneously favored in a
model selection sense, including the sum of neutrino masses, curvature,
evolving dark energy, and modified gravity. The complementarity of our
observables allows for constraints on modified gravity degrees of freedom that
are not simultaneously bounded with either probe alone, and up to a factor of
three improvement in the $S_8$ constraint in the extended cosmology compared to
KiDS alone.
