We present the discovery of four remote star clusters in M33 , one of which is of an extended nature .
Three of the clusters were discovered using survey data from the Isaac Newton Telescope Wide-Field Camera while one was discovered serendipitously in a deep image taken with the Hubble Space Telescope ’ s Advanced Camera for Surveys .
With projected radii of 38–113 arcmin ( 9.6–28.5 kpc for an assumed M33 distance of 870 kpc ) , these clusters lie significantly beyond all but one of the currently-confirmed clusters in M33 .
The clusters have magnitudes and colors consistent with their being old to intermediate-age globular clusters .
Indeed , they bear a strong resemblance to the outer halo GC population of the Milky Way and M31 in terms ( V-I ) _ { 0 } colours .
The three outermost clusters are projected on the far side of M33 with respect to M31 , an asymmetry that could suggest tidal interactions have affected M33 ’ s globular cluster distribution at large radii .