Abstract
We report the detection of a largely ionized very-high velocity cloud (VHVC;
$v_LSR\sim-350$ 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$_ødot$). 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.
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