Galaxy And Mass Assembly (GAMA): $mathbf{z sim 0}$ Galaxy Luminosity Function down to $mathbf{L sim 10^{6}~L_odot}$ via Clustering Based Redshift Inference

In this study we present a new experimental design using clustering-based redshift inference to measure the evolving galaxy luminosity function (GLF) down to the faintest possible limits, spanning 5.5 decades from $L sim 10^{11.5}$ to $ 10^6 ~ mathrm{L}_odot$. We use data from the Galaxy And Mass Assembly (GAMA) survey and the Kilo-Degree Survey (KiDS). We derive redshift distributions in bins of apparent magnitude to the limits of the GAMA-KiDS photometric catalogue: $m_r lesssim 23$; more than a decade beyond the limits of the GAMA spectroscopic redshift sample via clustering-based redshift inference. This technique uses spatial cross-correlation statistics for a reference set with known redshifts (in our case, the main GAMA sample) to derive the redshift distribution for the target ensemble. For the calibration of the redshift distribution we use a simple parametrisation with an adaptive normalisation factor over the interval $0.005 < z < 0.48$ to derive the clustering redshift results. We find that the GLF has a relatively constant power-law slope $alpha approx -1.2$ for $-17 lesssim M_r lesssim -13$, and then appears to steepen sharply for $-13 lesssim M_r lesssim -10$. 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 $z sim 0$ field galaxy population from the most luminous galaxies down to the GC scale.