The rest-frame optical (900nm) galaxy luminosity function at z~4-7:
  abundance matching points to limited evolution in the Mstar/Mhalo ratio at
  z>4
  We present the first determination of the galaxy luminosity function (LF) at
z~4, 5, 6 and 7 in the rest-frame optical at lambda_rest~900 nm (z' band). The
rest-frame optical light traces the content in low-mass evolved stars (~stellar
mass - Mstar), minimizing potential measurement biases for Mstar. Moreover it
is less affected by nebular line emission contamination and dust attenuation,
is independent of stellar population models, and can be probed up to z~8
through Spitzer/IRAC. Our analysis leverages the unique full depth Spitzer/IRAC
3.6um-to-8.0um data over the CANDELS/GOODS-N, CANDELS/GOODS-S and
COSMOS/UltraVISTA fields. We find that at absolute magnitudes M_z' fainter than
>-23 mag, M_z' linearly correlates with M_UV,1600. At brighter M_z', M_UV,1600
presents a turnover, suggesting that the stellar mass-to-light ratio
Mstar/L_UV,1600 could be characterised by a very broad range of values at high
stellar masses. Median-stacking analysis recovers a Mstar/L_z' roughly
independent on M_z' for M_z'>-23 mag, but exponentially increasing at brighter
magnitudes. We find that the evolution of the LF marginally prefers a pure
evolution in luminosity over a pure evolution in density, with the
characteristic luminosity decreasing by a factor ~5x between z~4 and z~7.
Direct application of the recovered Mstar/L_z' generates stellar mass functions
consistent with average measurements from the literature. Measurements of the
stellar-to-halo mass ratio at fixed cumulative number density show that it is
roughly constant with redshift for Mh>10^12Msun. This is also supported by the
fact that the evolution of the LF at 4<z<7 can be accounted for by a rigid
displacement in luminosity corresponding to the evolution of the halo mass from
abundance matching.
