20-24 March 2023
Haus H, Telegrafenberg
Europe/Berlin timezone

Mapping the deforming dark matter haloes of the Milky Way and the LMC with stellar streams

20 Mar 2023, 11:45
Haus H, Telegrafenberg

Haus H, Telegrafenberg

Potsdam, Germany
Contributed talk SESSION 1: From ground and space: motions, distances, chemistry and star formation measurements SESSION 1: From ground and space: motions, distances, chemistry and star formation measurements


Sophia Lilleengen (University of Surrey)


The ongoing merger of the Milky Way and the Large Magellanic Cloud (LMC) is deforming the dark matter haloes of both galaxies, effectively making these galaxies a local dark matter collider. Within this collider, stellar streams act as useful detectors as they are very sensitive to the gravitational potential, and span large parts of the Milky Way halo.
The Orphan-Chenab (OC) stream is particularly insightful as it spans the inner and outer Milky Way, and it passes close to the LMC (within 10kpc). In this talk, I will present the first models of the OC stream in the time-dependent halos of the Milky Way and the LMC that are described by basis function expansions of N-body simulations of the Milky Way-LMC passage. I will show how these deformations have an observable signature on the OC stream. In particular, we find that the Milky Way’s dipole has the most significant effect.
We do not currently have the tools to fit these deformations and ignoring them may result in biases. To test this, we fit mock streams evolved in these deforming potentials with current state-of-the-art stream models. Even though the MW is spherical in these mocks, we infer extremely large flattenings of the DM halos with q=0.6 and q=1.5. This shows that current measurements of the MW DM halo shape are likely biased and motivates the need for computationally efficient tools to describe these deformations. This work is an important first step in measuring the Milky Way’s mass profile over time.

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Primary author

Sophia Lilleengen (University of Surrey)

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