The Structure and Metallicity Gradient in the Extreme Outer Disk of NGC
  7793
  Studies of outer regions of spirals disks are fundamental to our
understanding of both the process of galaxy assembly and the subsequent secular
evolution of galaxies. In an earlier series of papers we explored the extent
and abundance gradient in the outer disk of NGC 300 and found an extended
purely exponential disk with a metallicity gradient which flattens off in the
outermost regions. We now continue the study of outskirts of pure disk spirals
with another Sculptor Group spiral, NGC 7793. Using Gemini Multi Object
Spectrograph camera at Gemini South, we trace the disk of NGC 7793 with star
counts out to ~9 scale lengths, corresponding to 11.5 kpc at our calibrated
distance of 3.61+/-0.53 Mpc. The outer disk of NGC 7793 shows no evidence of a
break in its light profile down to an effective surface brightness of ~30
mag/arcsec^2 (~3 mag/arcsec^2 deeper than what has been achieved with surface
photometry) and exhibits a non-negative abundance gradient within the radial
extent of our data.
