Unearthing foundations of a cosmic cathedral: searching the stars for M33’s halo

We use data from the Pan-Andromeda Archaeological Survey 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 disc whose connection to the recently discovered extended ‘disc substructure’ is ambiguous, and which may represent a ‘bona fide’ halo component. After first correcting for contamination from the Milky Way …