We have surveyed approximately 40 square degrees surrounding M33 with CFHT MegaCam/MegaPrime in the g and i filters out to a maximum projected radius from this galaxy of 50 kpc , as part of the Pan-Andromeda Archaeological Survey ( PAndAS ) .
Our observations are deep enough to resolve the top \sim 4 magnitudes of the red giant branch population in this galaxy .
We have previously shown that the disk of M33 is surrounded by a large , irregular , low-surface brightness substructure .
Here , we quantify the stellar populations and structure of this feature using the PAndAS data .
We show that the stellar populations of this feature are consistent with an old population with < [ Fe / H ] > \sim - 1.6 dex and an interquartile range in metallicity of \sim 0.5 dex .
We construct a surface brightness map of M33 that traces this feature to \mu _ { V } \simeq 33 mags arcsec ^ { -2 } .
At these low surface brightness levels , the structure extends to projected radii of \sim 40 kpc from the center of M33 in both the north-west and south-east quadrants of the galaxy .
Overall , the structure has an “ S-shaped ” appearance that broadly aligns with the orientation of the HI disk warp .
We calculate a lower limit to the integrated luminosity of the structure of -12.7 \pm 0.5 mags , comparable to a bright dwarf galaxy such as Fornax or Andromeda II and slightly less than 1 \% of the total luminosity of M33 .
Further , we show that there is tentative evidence for a distortion in the distribution of young stars near the edge of the HI disk that occurs at similar azimuth to the warp in HI .
The data also hint at a low-level , extended stellar component at larger radius that may be a M33 halo component .
We revisit studies of M33 and its stellar populations in light of these new results , and we discuss possible formation scenarios for the vast stellar structure .
Our favored model is that of the tidal disruption of M33 in its orbit around M31 .