Probing galaxy assembly bias with LRG weak lensing observations
  In Montero-Dorta et al. 2017, we show that luminous red galaxies (LRGs) from
the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) at $z\sim0.55$ can
be divided into two groups based on their star formation histories. So-called
fast-growing LRGs assemble $80\%$ of their stellar mass at $z\sim5$, whereas
slow-growing LRGs reach the same evolutionary state at $z\sim1.5$. We further
demonstrate that these two subpopulations present significantly different
clustering properties on scales of $\sim1 - 30 \mathrm{Mpc}$. Here, we measure
the mean halo mass of each subsample using the galaxy-galaxy lensing technique,
in the $\sim190\deg^2$ overlap of the LRG catalogue and the CS82 and CFHTLenS
shear catalogues. We show that fast- and slow-growing LRGs have similar lensing
profiles, which implies that they live in haloes of similar mass:
$\log\left(M_{\rm halo}^{\rm fast}/h^{-1}\mathrm{M}_{\odot}\right) =
12.85^{+0.16}_{-0.26}$ and $\log\left(M_{\rm halo}^{\rm
slow}/h^{-1}\mathrm{M}_{\odot}\right) =12.92^{+0.16}_{-0.22}$. This result,
combined with the clustering difference, suggests the existence of galaxy
assembly bias, although the effect is too subtle to be definitively proven
given the errors on our current weak-lensing measurement. We show that this can
soon be achieved with upcoming surveys like DES.
