In the \Lambda CDM paradigm the Galactic stellar halo is predicted to harbor the accreted debris of smaller systems .
To identify these systems , the H3 Spectroscopic Survey , combined with Gaia , is gathering 6D phase-space and chemical information in the distant Galaxy .
Here we present a comprehensive inventory of structure within 50 kpc from the Galactic center using a sample of 5684 giants at |b| > 40 ^ { \circ } and |Z| > 2 kpc .
We identify known structures including the high- \alpha disk , the in-situ halo ( disk stars heated to eccentric orbits ) , Sagittarius ( Sgr ) , Gaia -Sausage-Enceladus ( GSE ) , the Helmi Streams , Sequoia , and Thamnos .
Additionally , we identify the following new structures : ( i ) Aleph ( [ Fe/H ] = -0.5 ) , a low eccentricity structure that rises a surprising 10 kpc off the plane , ( ii , iii ) Arjuna ( [ Fe/H ] = -1.2 ) and I ’ itoi ( [ Fe/H ] < -2 ) , which comprise the high-energy retrograde halo along with Sequoia , and ( iv ) Wukong ( [ Fe/H ] = -1.6 ) , a prograde phase-space overdensity chemically distinct from GSE .
For each structure we provide [ Fe/H ] , [ \alpha /Fe ] , and orbital parameters .
Stars born within the Galaxy are a major component at |Z| \sim 2 kpc ( \approx 60 \% ) , but their relative fraction declines sharply to \lesssim 5 \% past 15 kpc .
Beyond 15 kpc , > 80 \% of the halo is built by two massive ( M _ { \star } \sim 10 ^ { 8 } -10 ^ { 9 } M _ { \odot } ) accreted dwarfs : GSE ( [ Fe/H ] = -1.2 ) within 25 kpc , and Sgr ( [ Fe/H ] = -1.0 ) beyond 25 kpc .
This explains the relatively high overall metallicity of the halo ( [ Fe/H ] \approx - 1.2 ) .
We attribute \gtrsim 95 \% of the sample to one of the listed structures , pointing to a halo built entirely from accreted dwarfs and heating of the disk .