LMC vs MW: Effects on the stellar & DM halo of the MW

Nicolas Garavito-CamargoU. Arizona

Gurtina Besla, Chervin Laporte, Facundo Gomez, Kathryn Johnston, Laura Watkins & Jeff Carlin

The LMC is the biggest perturber of the MW’s halo. Currently, just passed its pericenter.

ESA/

Gaia/

DPAC

50 kpc

LMC vs MW: Nico Garavito-Camargo

The LMC is the biggest perturber of the MW’s halo. Currently, just passed its pericenter.

ESA/

Gaia/

DPAC

50 kpc

Very rare configuration to find in cosmological simulations (Boylan-Kolchin+11 , Busha+11, Patel+17, Shao+18, )

LMC vs MW: Nico Garavito-Camargo

Besla+16, Mackey+16.See also: Balbinot et al 2015, Saha et al 2010.

The LMC is big!

LMC vs MW: Nico Garavito-Camargo

● LMC rotation curve:Total mass (<9 kpc): 1.7 x 1010 M

☉(van der Marel & Kallivayalil 2014)Total mass (<20 kpc): 3 x 1010 M

☉

● Baryon Fraction (3-5%):LMC M★: ~ 3x109M

☉ -> MDM0.5 - 1 x 1011 M

☉(van der Marel+09)

● Timing argument: 2.5x 1011 M☉

(Peñarrubia+16)

● In EAGLE simulation LMC with SMC are found to have ~3x1011M

☉ (Shao+18)

Besla+16, Mackey+16.See also: Balbinot et al 2015, Saha et al 2010.

The LMC is big! LMC Estimated mass: ~1011 M☉

LMC vs MW: Nico Garavito-Camargo

1. At what radius does the LMC affect the stellar & DM halo of the MW?

LMC vs MW: Nico Garavito-Camargo

1. At what radius does the LMC affect the stellar & DM halo of the MW?

2. What are the consequences (in density and kinematics) for the DM & stellar halo?

LMC vs MW: Nico Garavito-Camargo

1. At what radius does the LMC affect the stellar & DM halo of the MW?

2. What are the consequences (in density and kinematics) for the DM & stellar halo?

3. What are the observables of these effects?

LMC vs MW: Nico Garavito-Camargo

8 high-resolution N-body simulations1 of the LMC in a first infall scenario● LMC on first passage, infall DM Mass ~ 1011 M

☉

● MW DM halo initially spherical + MW Disk & Bulge

● MW mass Mvir= 1.2x1012M☉

● Two stellar halos density profiles (Xue,+15,

Hernitschek+18) added using a DM halo tagging

technique Laporte+13a, 13b.

Combined DM halo (LMC+MW) is not spherical,

oblate, prolate or triaxial.

1 N-body sims run with GADGET-3

Garav

ito-C

amarg

o, Be

sla et

. al in

prep

LMC vs MW: Nico Garavito-Camargo

Milky Way’s DM halo response & wake evolves in time.

LMC vs MW: Nico Garavito-Camargo

Garav

ito-C

amarg

o, Be

sla et

. al in

prep

Dark Matter halo response in the stellar halo is stronger at r>40 kpc.

LMC vs MW: Nico Garavito-CamargoGaravito-Camargo, Besla et. al in prep

LMC vs MW: Nico Garavito-CamargoGaravito-Camargo, Besla et. al in prep

Dark Matter halo response in the stellar halo is stronger at r>40 kpc.

LMC vs MW: Nico Garavito-CamargoGaravito-Camargo, Besla et. al in prep

Dark Matter halo response in the stellar halo is stronger at r>40 kpc.

LMC vs MW: Nico Garavito-CamargoGaravito-Camargo, Besla et. al in prep

Dark Matter halo response in the stellar halo is stronger at r>40 kpc.

The strength of the DM wake depends on the kinematics of the DM halo (Also found by Nicola Amorisco).

Isotropic Model Anisotropic ModelGaravito-Camargo, Besla et. al in prep

LMC vs MW: Nico Garavito-Camargo

Stellar Halo Kinematics: Tangential Velocity Dispersion responds to the LMC anisotropically.

LMC vs MW: Nico Garavito-Camargo

Garav

ito-C

amarg

o, Be

sla et

. al in

prep

Changing by as much as 20-30 km/s relative to the all-sky average.

The same is observed in the radial component.

Stellar halo kinematics as a tracer of the DM halo response.

LMC vs MW: Nico Garavito-Camargo

r

LMC vs MW: Nico Garavito-Camargo

Observational strategies to observe the DM halo response:At r>50 kpc and avoid Sgr.

Plot made using: GALSTREAMS (Mateu+17)

LMC vs MW: Nico Garavito-Camargo

Garav

ito-C

amarg

o, Be

sla et

. al in

prep

Observational strategies to observe the DM halo response:At r>50 kpc and avoid Sgr.

Plot made using: GALSTREAMS (Mateu+17)

LMC vs MW: Nico Garavito-Camargo

Garav

ito-C

amarg

o, Be

sla et

. al in

prep

Observational strategies to observe the DM halo response:At r>50 and avoid Sgr.

Plot made using: GALSTREAMS (Mateu+17)

Conclusions:LMC is massive and near pericenter, making it hard to study in existing cosmological simulations.

1. Preliminary work (idealized Nbody) shows that within 40 kpc the LMC’s impact is minimal.2. Outside 40 kpc, the LMC should leave an observational imprint, both trailing and leading its

current location. Imprints are both density enhancements and kinematic perturbations. 3. The kinematics of the stellar halo traces the DM halo response. 4. We are making predictions for observations. (If you are interested please come talk to me)

The time evolution of the DM halo potential owing to the LMC is also in progress.

LMC vs MW: Nico Garavito-Camargo: jngaravitoc@email.arizona.edu

Combined MW+LMC DM halo potential evolving in time.

The LMC orbit doesn’t change with LMC mass.