THE SHAPE AND PROFILE OF THE MILKY WAY HALO AS SEEN BY THE CANADA-FRANCE-HAWAII TELESCOPE LEGACY SURVEY

We use Canada-France-Hawaii Telescope Legacy Survey data for 170 deg(2), recalibrated and transformed to the Sloan Digital Sky Survey ugri photometric system, to study the distribution of near-turnoff main-sequence stars in the Galactic halo along four lines of sight to heliocentric distances of similar to 35 kpc. We find that the halo stellar number density profile becomes steeper at Galactocentric distances greater than R-gal similar to 28 kpc, with the power-law index changing from n(inner) = -2.62 +/- 0.04 to n(outer) = -3.8 +/- 0.1. In particular, we test a series of single power-law models and find them to be strongly disfavored by the data. The parameters for the best-fit Einasto profile are n = 2.2 +/- 0.2 and R-e = 22.2 +/- 0.4 kpc. We measure the oblateness of the halo to be q equivalent to c/a = 0.70 +/- 0.01 and detect no evidence of it changing across the range of probed distances. The Sagittarius stream is detected in the l = 173 degrees and b = -62 degrees direction as an overdensity of [Fe/H] similar to -1.5 dex stars at R-gal similar to 32 kpc, providing a new constraint for the Sagittarius stream and dark matter halo models. We also detect the Monoceros stream as an overdensity of [Fe/H] > -1.5 dex stars in the l = 232 degrees and b = 26 degrees direction at R-gal less than or similar to 25 kpc. In the two sight lines where we do not detect significant substructure, the median metallicity is found to be independent of distance within systematic uncertainties ([Fe/H] similar to -1.5 +/- 0.1 dex).