The Metal-poor Metallicity Distribution of the Ancient Milky Way

We present a low metallicity map of the Milky Way consisting $\sim$111,000 giants with $-3.5 \lesssim$ [Fe/H] $\lesssim -$0.75, based on public photometry from second data release SkyMapper survey. These stars extend out to $\sim$7kpc solar neighborhood and cover main Galactic stellar populations, including thick disk inner halo. Notably, this can reliably differentiate metallicities down $\sim -3.0$, thus provides an unprecedented view into ancient, metal-poor Way. Among more metal-rich in our sample ([Fe/H] $> -2.0$), we recover clear spatial dependence decreasing mean as function scale height that maps onto component When only considering very $< -$2), no such their $|Z|\sim7$ kpc. find distribution (MDF) most ($-3.0 <$ -2.3$) is well fit exponential profile slope $\Delta\log(N)/\Delta$[Fe/H] = 1.52$\pm$0.05, shifts 1.53$\pm$0.10 after accounting for target selection effects. For -2.3$, MDF largely insensitive $|Z|$ $\sim5$kpc, showing extremely are every galactic component.