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Subhalos-stream interaction in the presence of massive satellites

Presentation #502.02 in the session Galaxy Dynamics 3: Milky Way and Friends.

Published onJul 01, 2023
Subhalos-stream interaction in the presence of massive satellites

Dark matter subhalos potentially can be detected when they interact with stellar streams, leaving perturbations along the stream track. Massive in-falling satellites such as the Large Magellanic Cloud (LMC) displaces the host barycenter during the interaction, leading to a displacement in both position and velocity (reflex motion), which causes a north-south asymmetry in density and an anisotropy in radial velocity distribution. It also brings its own population of subhalos and induces a dark matter wake that could locally perturb the number density of subhalos, complicating efforts to interpret possible interaction signatures. Using the FIRE-2 zoomed cosmological baryonic simulations, we calculate the encounter rates between subhalos with masses 105-109 Msun and injected real Milky Way/simulated stellar streams under the influence of a LMC-like satellite. We integrate these streams in a smooth potential model around the first pericenter to explore the dependence of encounter rates on stream orbit and sky position. We find that the encounter rates can increase up to 3 fold in regions polar opposite to the LMC due to the reflex motion, and in regions around LMC due to influx of LMC subhalos and the DM wake. While the LMC drags in a large number of subhalos at infall, most of them are quickly destroyed by tides; the survivors account for only about 20% of the total subhalo population after the first pericenter passage of the LMC analog. We estimate encounter rates for all MW streams and provide predictions on where to observe tidal stream signatures of these encounters in the sky.

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