Evolution of planes of satellites Shi Shao ( ) Institute for - - PowerPoint PPT Presentation

• University of Durham

Small galaxies 2019, Durham — Shi Shao

Shi Shao (邵实) Institute for Computational Cosmology, Durham University

Evolution of planes of satellites

with Marius Cautun, Alis Deason, Adrian Jenkins, Carlos Frenk

• University of Durham

Small galaxies 2019, Durham — Shi Shao

3 6 60 120 180 240 300

• 60
• 30

30 60 Sagittarius LMC SMC Draco Ursa Minor Sculptor Sextans Carina Fornax Leo II Leo I

MW satellite positions and orbital poles

Leo II Leo I Draco UMinor Sextans Sagittarius LMC SMC Car Scu Frn

Minor axis Major axis c/a = 0.18

• University of Durham

Small galaxies 2019, Durham — Shi Shao

3 6 60 120 180 240 300

• 60
• 30

30 60 Sagittarius LMC SMC Draco Ursa Minor Sculptor Sextans Carina Fornax Leo II Leo I Sculptor‘

MW satellite positions and orbital poles

8 of the 11 classical satellites are co-rotating within 21.9° — highly anisotropic!!!

Shao, Cautun, Frenk 2019

• University of Durham

Small galaxies 2019, Durham — Shi Shao

• We use the EAGLE

hydrodynamical simulation.

• We use MW-mass

haloes to construct mock satellite catalogues.

c/a = 0.18

Comparison to simulations

Short lived Long lived

• MW-like-thin
• MW-like-orbits

• University of Durham

Small galaxies 2019, Durham — Shi Shao

For each, only ~1% satellite systems in the simulation are as rare as our MW.

0.0 0.1 0.2 0.3 PDF 0° 10° 20° 30° 40° 50° 60° 70° 80°

• pening angle for 8 rotating Sats

MW

EAGLE

MW−like−orbits

0.0 0.2 0.4 0.6 0.8 1.0 c/a 0.0 0.1 0.2 PDF 0.0 0.2 0.4 0.6 0.8 1.0

MW

MW−like−thin

EAGLE

Comparison to simulations

• University of Durham

Small galaxies 2019, Durham — Shi Shao

~1,000,000 EAGLE galaxies in 100 Mpc3 ~2000 MW-mass with M200 ∈[0.5, 2] x 1012 M⊙ + Sats orbitally thin

Find ‘the One’ in Eagle matrix!

+ Sats perpendicular to their central + LMC (with SMC)

And then you find …

• University of Durham

Small galaxies 2019, Durham — Shi Shao

• University of Durham

Small galaxies 2019, Durham — Shi Shao

• Disc edge-on
• Sat plane edge-on
• Disc edge-on
• Sat plane face-on

• University of Durham

Small galaxies 2019, Durham — Shi Shao

• Disc edge-on
• Sat plane edge-on
• Disc edge-on
• Sat plane face-on

• University of Durham

Small galaxies 2019, Durham — Shi Shao

• Disc edge-on
• Sat plane edge-on
• Disc edge-on
• Sat plane face-on

• University of Durham

Small galaxies 2019, Durham — Shi Shao

0.1 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.1 1.0 R / R200 0.0 0.2 0.4 0.6 0.8 1.0 cos θC−H 90° 80° 70° 60° 50° 40° 30° 20° 0° 10 20 30 40 60 100 200 R [Kpc]

Inner halo is perfectly aligned with the disc Outer halo is twisted

A twisted MW halo?

10 8 6 4 2 0.0 0.2 0.4 0.6 0.8 1.0 10 8 6 4 2 Lookback time [Gyr] 0.0 0.2 0.4 0.6 0.8 1.0 Misalignment angle 90° 80° 70° 60° 50° 40° 30° 20° 0° 1.5 1 0.5 0.2 Redshift

Ldisc (Stars within 10 kpc) ê3; z=0 (DM within R200)

Shao, Cautun, Deason, Frenk in prep.

Twisted halo not due to “disc flip”

Halo varies more than the disc

• University of Durham

Small galaxies 2019, Durham — Shi Shao

The awakening (Zoom-in) of the One

• University of Durham

Small galaxies 2019, Durham — Shi Shao

MagPie simulations

600 Kpc

199 z = 0.00 t = 0.00 Gyr c/a, Top 11 = 0.23 c/a, All 20 = 0.38 XZ

600 Kpc

YZ

Preliminary!

• University of Durham

Small galaxies 2019, Durham — Shi Shao

MagPie simulations

600 Kpc

199 z = 0.00 t = 0.00 Gyr c/a, Top 11 = 0.23 c/a, All 20 = 0.38 XZ

600 Kpc

YZ

4 6 8 10 log10(M* / MO

• )

1 10 100 N (> M*)

MagPie EAGLE AU Lv4 AU Lv3 APOST MW M31

Sats stellar mass function

Preliminary!

Small galaxies 2019, Durham — Shi Shao

• University of Durham

Conclusions

• 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

• University of Durham

Orbital evolution of LMC-mass sat.

• Halo shape is not determined by massive sat.

10 8 6 4 2 0.0 0.2 0.4 0.6 0.8 1.0 10 8 6 4 2 Lookback time [Gyr] 0.0 0.2 0.4 0.6 0.8 1.0 Misalignment angle 90° 80° 70° 60° 50° 40° 30° 20° 0° 1.5 1 0.5 0.2 Redshift

Ldisc (Stars within 10 kpc) ê3; z=0 (DM within R200)

Halo varies more than the

10 8 6 4 2 100 200 300 400 10 8 6 4 2 Lookback time [Gyr] 100 200 300 400 DistanceMW−LMC [pkpc] R200 3 2 1 0.5 0.2 Redshift