2011ApJ...731....4S

We use Canada-France-Hawaii Telescope Legacy Survey data for 170 deg², 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 ∼35 kpc. We find that the halo stellar number density profile becomes steeper at Galactocentric distances greater than R_gal∼ 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 ≡ 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° and b = -62° direction as an overdensity of [Fe/H] ∼ -1.5 dex stars at R_gal∼ 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° and b = 26° direction at R_gal≲ 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] ∼ -1.5 ± 0.1 dex).