MATs (Monday Afternoon Talks), 10/16/2023 — Speakers: Jesse Han & Arpit Arora

Monday October 16, 2023 3:00 pm

MATs (Monday Afternoon Talks)

3:00pm – 3:30pm, Jesse Han
A Galactic Mystery “Unwarped”
The outer disk of the Milky Way Galaxy is warped and flared. Several mechanisms have been proposed to explain these phenomena, but none have quantitatively reproduced both features. Recent work has demonstrated that the Galactic stellar halo is tilted with respect to the disk plane, suggesting that at least some component of the dark matter halo may also be tilted. Here we show that a dark halo tilted in the same direction as the stellar halo can induce a warp and flare in the Galactic disk at the same amplitude and orientation as the data. In our model the warp is visible in both the gas and stars of all ages, which is consistent with the breadth of observational tracers of the warp. These results, in combination with data in the stellar halo, provide compelling evidence that our Galaxy is embedded in a tilted dark matter halo.

3:30pm – 4:00pm, Arpit Arora
Dark matter, dynamics, and disequilibria in the Milky Way
The nature of DM manifests at galactic scales, where we impose constraints by modeling star and gas orbits, typically in the high-density central regions of the MW and its satellites. In these regions, the DM physics is sub-dominant to baryonic processes. Additionally, modeling techniques often rely on assuming some symmetry and/or equilibrium for the MW halo. However, the MW’s halo is asymmetric due to accretion along filamentary structures and in disequilibrium, courtesy of the in-falling LMC in the outer halo and the Sagittarius dwarf in the disc. In this talk, I will discuss; 1) a novel technique to model time-evolving MW potential, capturing deformations induced by in-falling massive satellites using Basis Function Expansions; 2) an innovative application of this model to understand anisotropic boosts in subhalo-stream interactions driven by the LMC. Finally, I will explore the prospects of constraining DM by out-of-equilibrium modeling in the outermost, DM-dominant regions of the MW.


Hosts: Minghao Yue, Daniele Michilli


  • Jesse Han, CfA Harvard
  • Arpit Arora, University of Pennsylvania