Chemical Mapping of the Milky Way With The Canada-France Imaging Survey:
  A Non-parametric Metallicity-Distance Decomposition of the Galaxy
  We present the chemical distribution of the Milky Way, based on 2,900$\, {\rm
deg^2}$ of $u$-band photometry taken as part of the Canada-France Imaging
Survey. When complete, this survey will cover 10,000$\, {\rm deg^2}$ of the
Northern sky. By combing the CFHT $u$-band photometry together with SDSS and
Pan-STARRS $g,r,$ and $i$, we demonstrate that we are able to measure reliably
the metallicities of individual stars to $\sim 0.2$ dex, and hence additionally
obtain good photometric distance estimates. This survey thus permits the
measurement of metallicities and distances of the dominant main-sequence
population out to approximately 30 kpc, and provides much higher number of
stars at large extraplanar distances than have been available from previous
surveys. We develop a non-parametric distance-metallicity decomposition
algorithm and apply it to the sky at $30\deg < |b| < 70\deg$ and to the North
Galactic Cap. We find that the metallicity-distance distribution is
well-represented by three populations whose metallicity distributions do not
vary significantly with vertical height above the disk. As traced in
main-sequence stars, the stellar halo component shows a vertical density
profile that is close to exponential, with a scale height of around 3 kpc. This
may indicate that the inner halo was formed partly from disk stars ejected in
an ancient minor merger.
