# The Discovery and Origin of A Very-High Velocity Cloud Toward M33

## TL;DR

This paper reports the discovery of a very-high velocity cloud near M33, analyzing its properties and potential origins, and concludes it could be a halo structure related to the Magellanic Stream or M33 itself.

## Contribution

First detection of a highly ionized VHVC toward M33 with detailed velocity and metallicity measurements, exploring its possible origins and connections.

## Key findings

- VHVC has a metallicity of ~0.28 Z_sun.
- Velocities and ionic column densities are relatively uniform across sightlines.
- Possible origins include MW CGM, Wright's Cloud, or M33's warp.

## Abstract

We report the detection of a largely ionized very-high velocity cloud (VHVC; $v_{\rm LSR}\sim-350$ km/s) toward M33 with the Hubble Space Telescope/Cosmic Origin Spectrograph. The VHVC is detected in OI, CII, SiII, and SiIII absorption along five sightlines separated by ~0.06-0.4 degree. On sub-degree scales, the velocities and ionic column densities of the VHVC remain relatively smooth with standard deviations of +/-14 km/s and +/-0.15 dex between the sightlines, respectively. The VHVC has a metallicity of [OI/HI]=-0.56+/-0.17 dex (Z=0.28+/-0.11 Z$_{\odot}$). Despite the position-velocity proximity of the VHVC to the ionized Magellanic Stream, the VHVC's higher metallicity makes it unlikely to be associated with the Stream, highlighting the complex velocity structure of this region of sky. We investigate the VHVC's possible origin by revisiting its surrounding HI environment. We find that the VHVC may be: (1) a MW CGM cloud, (2) related to a nearby HI VHVC -- Wright's Cloud, or (3) connected to M33's northern warp. Furthermore, the VHVC could be a bridge connecting Wright's Cloud and M33's northern warp, which would make it a Magellanic-like structure in the halo of M33.