Work

The Distant Milky Way Halo from the Southern Hemisphere: Characterization of the LMC-induced Dynamical Friction Wake*

Year: 2025

Type: article

Abstract: The infall of the Large Magellanic Cloud (LMC) into the Milky Way’s halo impacts the distribution of stars and dark matter (DM) in our Galaxy. Mapping the observational consequences of this encounter can inform us about the properties of both galaxies, details of their interaction, and possibly distinguish between different DM models. N-body simulations predict a localized overdensity trailing the LMC’s orbit both in baryonic and DM, known as the wake. We collected wide-field, deep near-infrared, and optical photometry using VIRCAM and DECam across four fields along the expected wake, covering the sky region expected to span most of its predicted density contrast. We identify over 400 stars comprising two different tracers, near main-sequence turnoff stars and red giants, which map the halo between 60 and 100 kpc, deriving stellar halo densities as a function of sky position and Galactocentric radius. We detect (1) a break in the halo radial density profile at 70 kpc not seen in northern halo studies and (2) a clear halo overdensity starting also at 70 kpc, with density contrast increasing steadily toward the expected current location of the wake. If this overdensity is the LMC wake, its peak density contrast is as pronounced as the most massive LMC model considered. Contamination from unidentified substructures may bias our wake detections, so wider-area surveys with similar depth are needed for confirmation.

Source: The Astrophysical Journal

DOI: 10.3847/1538-4357/adbf08