Stellar surface density profiles in the observed fields versus projected (left) and deprojected (right) radius. The open squares and filled dots show the stellar surface density in the SE1-SE3, and NW4-NW6 fields, respectively. Star symbols indicate the density at large radii when field NW7 is also included. The M 33 stellar disc extends out to 40′, while at larger radii there is a clear change in the surface density. A power-law profile (Rⁿ) is fitted to the data in the left panel to investigate the presence of a stellar halo. We did not attempt to fit the star points because of the anomalous overdensity in field NW7. An extended disc component (e^−R/h) is fitted to the data in the right panel. The best-fit parameters for each model are displayed in the panels.