The Galaxy Luminosity Function via Clustering Based Redshift Inference: can we find the bottom of the galaxy population?

The galaxy luminosity function (GLF) is a basic descriptor of the galaxy population and its evolution though the history of the Universe. I will present a new experimental design using clustering-based redshift inference to measure the evolving galaxy luminosity function. The idea is to exploit the fact that galaxies are not uniformly distributed through space; instead are strongly clustered and it is therefore possible to infer the statistical distribution of distances. We derive the GLF using data from the Galaxy And Mass Assembly (GAMA) survey and the Kilo-Degree Survey (KiDS) to the limits of the GAMA-KiDS photometric catalogue: m_r ~ 23; more than a decade in luminosity beyond the limits of the GAMA spectroscopic redshift sample. We find that the GLF has a relatively constant power-law slope α ≈ −1.2 for M_r < −13, and then appears to steepen sharply. This upturn appears to be where Globular Clusters (GCs) take over to dominate the source counts as a function of luminosity. Thus we have mapped the GLF across the full range of the z~0 field galaxy population from the most luminous galaxies down to the GC scale.