Deep H{\alpha} Observations of NGC 253: a Very Extended and Possibly
  Declining Rotation Curve?
  This study presents a deep H{\alpha} kinematical analysis of the Sculptor
Group galaxy NGC253. The Fabry-Perot data were taken with the 36-cm Marseille
Telescope in La Silla, Chile, using an EMCCD detector. Typical emission
measures of ~0.1 cm^-6 pc are reached. The observations allow the detection of
the Diffuse Ionized Gas component through [N II] emission at very large radii
of 11.5', 12.8' and 19.0', on the receding side of the galaxy. No H{\alpha}
emission is observed at radii larger than the neutral component (11.5'). The
very extended rotation curve confirms previous results and shows signs of a
significant decline, on the order of 30 per cent vmax . Using the rotation
data, mass models are constructed with and without the outer [N II] data
points, and similar results are found. The declining part of the rotation curve
is very well modeled, and seems to be truly declining.
