We conduct a detailed lensing , dynamics and stellar population analysis of nine massive lens early-type galaxies ( ETGs ) from the X-Shooter Lens Survey ( XLENS ) .
Combining gravitational lensing constraints from HST imaging with spatially-resolved kinematics and line-indices constraints from VLT X-Shooter ( XSH ) spectra , we infer the low-mass slope and the low cut-off mass of the stellar Initial Mass Function ( IMF ) : x _ { 250 } = 2.37 ^ { +0.12 } _ { -0.12 } and M _ { \mathrm { low } , 250 } = 0.131 ^ { +0.023 } _ { -0.026 } M _ { \odot } , respectively , for a reference point with \sigma _ { \star } \equiv 250 \mathrm { km s ^ { -1 } } and R _ { eff } \equiv 10 kpc .
All the XLENS systems are consistent with an IMF slope steeper than Milky Way-like .
We find no significant correlations between IMF slope and any other quantity , except for an anti-correlation between total dynamical mass density and low-mass IMF slope at the 87 % CL [ dx / d \log ( \rho ) = -0.19 ^ { +0.15 } _ { -0.15 } ] .
This anti-correlation is consistent with the low redshift lenses found by Smith et al .
( 2015 ) that have high velocity dispersions and high stellar mass densities but surprisingly shallow IMF slopes .