The LMC: Past, Present and Future Marius Cautun (Leiden Obs. / - PowerPoint PPT Presentation

The LMC: Past, Present and Future Marius Cautun (Leiden Obs. / Durham Univ.*) Shi Shao, Alis Deason, Carlos Frenk, Stuart McAlpine and Tom Theuns Small Galaxies, Cosmic Questions Durham Shao, MC+ (2018b) — MNRAS, arXiv:1803.07269 2 August 2019 MC+ (2019) — MNRAS, arXiv:1809.09116

The Large Magellanic Cloud • The brightest MW satellite. • Unusually massive for a MW mass galaxy (expected ~10% of similarly sized galaxies). • Has 5% of the MW stellar mass (van der Marel + 2002), but potentially 25% of the total mass (Pennarubia+ 2016) Credit: AAO / ROE. Marius Cautun LMC: Past, Present and Future 2

The EAGLE galaxy formation simulation EAGLE matches the observations for: • Galaxy mass function • Galaxy sizes • Galaxy morphologies Schaye+ 2015 Marius Cautun LMC: Past, Present and Future 3

The sample of LMC-sized dwarfs 11 Number Stellar mass selected LMC-analogues: 0 10 20 30 40 M ⋆ = [1 − 4] × 10 9 M ⊙ 10 • ) log 10 (M* / M O Three samples: • Field, i.e. dwarfs that are central galaxies 9 • Satellites • Satellites of MW-mass hosts 8 10 11 12 13 log 10 (M 200 / M O • ) Shao, MC+ 2018 Marius Cautun LMC: Past, Present and Future 4

The LMC’s total mass • LMC was accreted about ~1.5 Gyrs ago when it had a ~10% lower stellar mass than today: M ⋆ = 2.4 × 10 9 M ⊙ • Abundance matching (Moster + 2013): M 200 = 1.8 +0.5 − 0.3 × 10 11 M ⊙ • EAGLE all LMC-sized dwarfs : M 200 = 2.0 +0.6 − 0.5 × 10 11 M ⊙ • EAGLE LMCs with an SMC-sized satellite: M 200 = 3.2 +1.0 − 0.9 × 10 11 M ⊙ (only 2% have an SMC-sized satellite) Shao+ 2018, MC+ (2019) Marius Cautun LMC: Past, Present and Future 5

The colour distribution 0.20 0.20 Field Satellites: all Satellites: MW-mass 0.15 0.15 PDF 0.10 0.10 0.05 0.05 LMC M33 0.00 0.00 0.0 0.0 0.0 0.2 0.2 0.2 0.4 0.4 0.4 0.6 0.6 0.6 0.8 0.8 0.8 1.0 1.0 1.0 g - r Shao, MC+ 2018 Marius Cautun LMC: Past, Present and Future 6

The colour distribution 1.0 Number 0 5 10 15 20 Field Satellite 0.8 g - r 0.6 0.4 0.2 10 11 12 13 14 15 log 10 (M 200 / M O • ) Shao, MC+ 2018 Marius Cautun LMC: Past, Present and Future 7

The colour distribution 1.0 Number 1.0 1.0 7 Gyr 0 5 10 15 20 6 Gyr 5 Gyr Field Satellite 4 Gyr 0.8 0.8 0.8 3 Gyr 2 Gyr 1 Gyr Fraction of red 0 Gyr 0.6 0.6 g - r 0.6 0.4 0.4 0.4 0.2 0.2 0.2 0.0 0.0 10 11 12 13 14 15 11 11 12 12 13 13 14 14 log 10 (M 200 / M O • ) log 10 (M 200 / M O • ) Shao, MC+ 2018 Marius Cautun LMC: Past, Present and Future 8

Bluer LMC-mass dwarfs in MW-mass host Redshift 0 3 2 1.5 1 0.5 0.2 0 0.8 600 600 0.20 Red satellite t infall 500 500 Gas fraction (< r 1/ 2 ) 0.6 0.15 Distance [kpc] 400 400 g - r 0.4 300 300 0.10 R 50 200 200 0.2 0.05 100 100 R 200 0.0 7.0 0.00 0.0 0.0 0 0 7.0 10 8 6 4 2 0 0.8 10 8 6 4 2 0 Lookback time [Gyr] Lookback time [Gyr] Shao, MC+ 2018 Marius Cautun LMC: Past, Present and Future 9

Bluer LMC-mass dwarfs in MW-mass host Most LMC-mass satellites were accreted in the last 7 Gyrs, much more recently than the MW classical satellites. This is because: • It takes longer for massive satellites to grow. LMC M33 • Enhanced dynamical friction => rapid orbital decay and merger with their central galaxy. Shao, MC+ 2018a, Shao, MC+ 2018b Marius Cautun LMC: Past, Present and Future 10

What is the LMC fate? — low LMC mass — • Light LMC: LMC M LMC 200 = 0.5 × 10 11 M ⊙ Andromeda MC+ 2019a Marius Cautun LMC: Past, Present and Future 11

What is the LMC fate? — current values of LMC mass — • Fiducial LMC: 200 = 2.5 × 10 11 M ⊙ M LMC t merger = 2.7 ± 1.0 Gyrs • Light LMC: M LMC 200 = 0.5 × 10 11 M ⊙ MC+ 2019a Marius Cautun LMC: Past, Present and Future 12

What are the consequences of a MW-LMC merger? Investigate similar mergers in EAGLE: Select mergers that took place between 1 and 8 Gyrs ago. Require that the LMC-analogue has the LMC’s stellar mass. Match the MW-analogue to the following present day properties of the MW: 1. Halo mass 2. Supermassive black hole mass 3. Cold gas mass 8 MW—LMC analogues Credit: Rudiger Pakmor Marius Cautun LMC: Past, Present and Future 13

The MW supermassive black hole MC+ 2019a Marius Cautun LMC: Past, Present and Future 14

The MW supermassive black hole MC+ 2019a Marius Cautun LMC: Past, Present and Future 15

The MW stellar halo MC+ 2019a Marius Cautun LMC: Past, Present and Future 16

The MW stellar halo MC+ 2019a Marius Cautun LMC: Past, Present and Future 17

The merger aftermath for the stellar halo Marius Cautun LMC: Past, Present and Future 18

1.0 Number 0 5 10 15 20 Summary Field Satellite 0.8 • The presence of the SMC suggests that the LMC has a very g - r 0.6 massive halo for its stellar mass. M 200 = 3 ± 1 × 10 11 M ⊙ 0.4 • LMC-mass dwarfs in MW-mass hosts are bluer than isolated 0.2 analogues due to enhanced SF and long quenching timescales. 10 11 12 13 14 15 log 10 (M 200 / M O • ) • If the LMC is as massive as recently estimated, it will merge with the MW in ~2.5 Gyrs. • Despite its puny stellar mass, the LMC collision will have large effects on our galaxy, increasing by many factors the mass of the central supermassive black hole and that of the stellar halo. Marius Cautun Return to normality 19