• • • University of Durham Evolution of planes of satellites Shi Shao ( 邵实 ) Institute for Computational Cosmology, Durham University with Marius Cautun, Alis Deason, Adrian Jenkins, Carlos Frenk Small galaxies 2019, Durham — Shi Shao
• • MW satellite positions and orbital poles • University of Durham Major axis c/a = 0.18 Leo II Leo I 60 Draco UMinor Sextans Sagittarius 30 Minor axis LMC Fornax SMC Car 0 300 240 120 180 60 Scu 6 0 3 Frn 0 Carina Ursa Minor Sculptor LMC SMC Sagittarius Draco Leo II -30 Leo I Sextans -60 Small galaxies 2019, Durham — Shi Shao
• • MW satellite positions and orbital poles • University of Durham 60 30 Fornax 0 300 240 120 180 60 6 0 3 Sculptor‘ 0 Carina 8 of the 11 classical satellites Ursa Minor Sculptor LMC are co-rotating within 21.9° SMC Sagittarius — highly anisotropic!!! Draco Leo II -30 Leo I Shao, Cautun, Frenk 2019 Sextans -60 Small galaxies 2019, Durham — Shi Shao
• MW-like-thin • MW-like-orbits • • • University of Durham Short lived Long lived Comparison to simulations c/a = 0.18 • We use the EAGLE hydrodynamical simulation. • We use MW-mass haloes to construct mock satellite catalogues. Small galaxies 2019, Durham — Shi Shao
• • Comparison to simulations • University of Durham 0.2 0.3 EAGLE EAGLE MW − like − thin MW − like − orbits 0.2 PDF PDF 0.1 0.1 MW MW 0.0 0.0 0 ° 10 ° 20 ° 30 ° 40 ° 50 ° 60 ° 70 ° 80 ° 0.0 0.0 0.2 0.2 0.4 0.4 0.6 0.6 0.8 0.8 1.0 1.0 opening angle for 8 rotating Sats c/a For each, only ~1% satellite systems in the simulation are as rare as our MW. Small galaxies 2019, Durham — Shi Shao
• • Find ‘the One’ in Eagle matrix! • University of Durham ~1,000,000 EAGLE galaxies in 100 Mpc 3 ~2000 MW-mass with M 200 ∈ [0.5, 2] x 10 12 M ⊙ + Sats orbitally thin + Sats perpendicular to their central + LMC (with SMC) And then you find … Small galaxies 2019, Durham — Shi Shao
• • • University of Durham Small galaxies 2019, Durham — Shi Shao
• • • • Disc edge-on • Disc edge-on University of Durham • Sat plane edge-on • Sat plane face-on • Small galaxies 2019, Durham — Shi Shao
• • • • Disc edge-on • Disc edge-on University of Durham • Sat plane edge-on • Sat plane face-on • Small galaxies 2019, Durham — Shi Shao
• • • • Disc edge-on • Disc edge-on University of Durham • Sat plane edge-on • Sat plane face-on Small galaxies 2019, Durham — Shi Shao
A twisted MW halo? • • • University of Durham R [Kpc] Redshift 10 20 30 40 60 100 200 1.5 1 0.5 0.2 0 1.0 1.0 0 ° 1.0 1.0 0 ° 20 ° Inner halo is 20 ° 30 ° perfectly aligned 30 ° L disc (Stars within 10 kpc) 0.8 0.8 with the disc 0.8 0.8 40 ° 40 ° Misalignment angle 50 ° 50 ° cos θ C − H 0.6 0.6 0.6 0.6 Twisted halo not due to “disc flip” ê 3; z=0 (DM within R 200 ) 60 ° 60 ° 0.4 0.4 0.4 0.4 70 ° 70 ° 0.2 0.2 0.2 0.2 80 ° 80 ° Halo varies more than the disc Outer halo is twisted 0.0 0.0 90 ° 0.0 0.0 90 ° 10 10 8 8 6 6 4 4 2 2 0 0 0.1 0.1 1.0 1.0 Lookback time [Gyr] R / R 200 Shao, Cautun, Deason, Frenk in prep. Small galaxies 2019, Durham — Shi Shao
The awakening (Zoom-in) of the One • • • University of Durham Small galaxies 2019, Durham — Shi Shao
• • Preliminary! MagPie simulations • University of Durham 199 XZ YZ z = 0.00 t = 0.00 Gyr c/a, Top 11 = 0.23 c/a, All 20 = 0.38 600 Kpc 600 Kpc Small galaxies 2019, Durham — Shi Shao
• • Preliminary! MagPie simulations • University of Durham Sats stellar mass function 100 199 XZ YZ MagPie z = 0.00 EAGLE t = 0.00 Gyr AU Lv4 c/a, Top 11 = 0.23 AU Lv3 APOST c/a, All 20 = 0.38 MW M31 � N (> M*) 10 1 4 6 8 10 600 Kpc 600 Kpc log 10 (M* / M O • ) Small galaxies 2019, Durham — Shi Shao
• • • Conclusions University of Durham • 8 out of the 11 MW classical satellites have roughly co-planar orbits. • This is atypical in LCDM, with only ~1% of EAGLE systems showing a similarly high degree of co-rotation. • The satellite rotation plane is very well aligned with the shape of the DM halo —> can infer the orientation of MW dark halo. • In the MW, the satellite rotation plane is perpendicular to the MW disc —> MW dark halo is twisted. • The twist is due to changes in the orientation of the MW dark halo due to cosmic web accretion. • Stay tuned for more MagPie results! Small galaxies 2019, Durham — Shi Shao
• • • Orbital evolution of LMC-mass sat. University of Durham Redshift Redshift 1.5 1 0.5 0.2 0 3 2 1 0.5 0.2 0 400 400 1.0 1.0 0 ° 20 ° 30 ° L disc (Stars within 10 kpc) 0.8 0.8 300 300 40 ° Distance MW − LMC [pkpc] Misalignment angle 50 ° 0.6 0.6 ê 3; z=0 (DM within R 200 ) 200 200 60 ° 0.4 0.4 70 ° R 200 100 100 0.2 0.2 80 ° Halo varies more than the 0.0 0.0 90 ° 0 0 10 10 8 8 6 6 4 4 2 2 0 0 10 10 8 8 6 6 4 4 2 2 0 0 Lookback time [Gyr] Lookback time [Gyr] • Halo shape is not determined by massive sat. Small galaxies 2019, Durham — Shi Shao
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