The Rest-frame Optical (900 nm) Galaxy Luminosity Function at z ∼ 4–7: Abundance Matching Points to Limited Evolution in the MSTAR/MHALO Ratio at z ≥ 4

Abstract

Abstract We present the first determination of the galaxy luminosity function (LF) at z ∼ 4, 5, 6, and 7, in the rest-frame optical at (z′ band). The rest-frame optical light traces the content in low-mass evolved stars (∼stellar mass—M *), minimizing potential measurement biases for M *. 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 3.6–8.0 μm data over the CANDELS/GOODS-N, CANDELS/GOODS-S, and COSMOS/UltraVISTA fields. We find that, at absolute magnitudes where is fainter than mag, linearly correlates with . At brighter , presents a turnover, suggesting that the stellar mass-to-light ratio could be characterized by a very broad range of values at high stellar masses. Median-stacking analyses recover an roughly independent on for mag, but exponentially increasing at brighter magnitudes. We find that the evolution of the LF marginally prefers a pure luminosity evolution over a pure density evolution, with the characteristic luminosity decreasing by a factor of between z ∼ 4 and z ∼ 7. Direct application of the recovered 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 . This is also supported by the fact that the evolution of the LF at can be accounted for by a rigid displacement in luminosity, corresponding to the evolution of the halo mass from abundance matching.