The Galactic stellar halo is predicted to have formed at least partially from the tidal disruption of accreted dwarf galaxies .
This assembly history should be detectable in the orbital and chemical properties of stars .
The H3 Survey is obtaining spectra for 200,000 stars , and , when combined with Gaia data , is providing detailed orbital and chemical properties of Galactic halo stars .
Unlike previous surveys of the halo , the H3 target selection is based solely on magnitude and Gaia parallax ; the survey therefore provides a nearly unbiased view of the entire stellar halo at high latitudes .
In this paper we present the distribution of stellar metallicities as a function of Galactocentric distance and orbital properties for a sample of 4232 kinematically-selected halo giants to 100 kpc .
The stellar halo is relatively metal-rich , \langle [ Fe/H ] \rangle = -1.2 , and there is no discernable metallicity gradient over the range 6 < R _ { gal } < 100 kpc .
However , the halo metallicity distribution is highly structured including distinct metal-rich and metal-poor components at R _ { gal } < 10 kpc and R _ { gal } > 30 kpc , respectively .
The Sagittarius stream dominates the metallicity distribution at 20 - 40 kpc for stars on prograde orbits .
The Gaia -Enceladus merger remnant dominates the metallicity distribution for radial orbits to \approx 30 kpc .
Metal-poor stars with [ Fe/H ] < -2 are a small population of the halo at all distances and orbital categories .
We associate the ‘ ‘ in-situ ’ ’ stellar halo with stars displaying thick-disk chemistry on halo-like orbits ; such stars are confined to |z| < 10 kpc .
The majority of the stellar halo is resolved into discrete features in orbital-chemical space , suggesting that the bulk of the stellar halo formed from the accretion and tidal disruption of dwarf galaxies .
The relatively high metallicity of the halo derived in this work is a consequence of the unbiased selection function of halo stars , and , in combination with the recent upward revision of the total stellar halo mass , implies a Galactic halo metallicity that is typical for its mass .