# The Pisces Plume and the Magellanic Wake

## TL;DR

This study characterizes the Pisces Overdensity as a long, diffuse stellar plume aligned with the Magellanic Stream, and suggests it is a Magellanic wake caused by the Magellanic Clouds' infall, based on observational data and simulations.

## Contribution

It provides the first detailed observational and simulation-based evidence linking the Pisces Overdensity to the Magellanic wake phenomenon.

## Key findings

- Pisces appears as a broad, elongated plume from 40 to 110 kpc.
- Velocity distribution of Pisces stars is broad and offset to negative velocities.
- Properties of Pisces match predictions for the Magellanic wake.

## Abstract

Using RR Lyrae stars in the Gaia Data Release 2 and Pan-STARRS1 we study the properties of the Pisces Overdensity, a diffuse sub-structure in the outer halo of the Milky Way. We show that along the line of sight, Pisces appears as a broad and long plume of stars stretching from 40 to 110 kpc with a steep distance gradient. On the sky Pisces's elongated shape is aligned with the Magellanic Stream. Using follow-up VLT FORS2 spectroscopy, we have measured the velocity distribution of the Pisces candidate member stars and have shown it to be as broad as that of the Galactic halo but offset to negative velocities. Using a suite of numerical simulations, we demonstrate that the structure has many properties in common with the predicted behaviour of the Magellanic wake, i.e. the Galactic halo overdensity induced by the in-fall of the Magellanic Clouds.