We use data from the Pan-Andromeda Archaeological Survey ( PAndAS ) to search for evidence of an extended halo component belonging to M33 ( the Triangulum Galaxy ) .
We identify a population of red giant branch ( RGB ) stars at large radii from M33 ’ s disk whose connection to the recently discovered extended “ disk substructure ” is ambiguous , and which may represent a “ bona-fide ” halo component .
After first correcting for contamination from the Milky Way foreground population and misidentified background galaxies , we average the radial density of RGB candidate stars over circular annuli centered on the galaxy and away from the disk substructure .
We find evidence of a low-luminosity , centrally concentrated component that is everywhere in our data fainter than \mu _ { V } \sim 33 mag arcsec ^ { -2 } .
The scale length of this feature is not well constrained by our data , but it appears to be of order r _ { exp } \sim 20 kpc ; there is weak evidence to suggest it is not azimuthally symmetric .
Inspection of the overall CMD for this region that specifically clips out the disk substructure reveals that this residual RGB population is consistent with an old population with a photometric metallicity of around [ Fe/H ] \sim -2 dex , but some residual contamination from the disk substructure appears to remain .
We discuss the likelihood that our findings represent a bona-fide halo in M33 , rather than extended emission from the disk substructure .
We interpret our findings in terms of an upper limit to M33 ’ s halo that is a few percent of its total luminosity , although its actual luminosity is likely much less .