The red supergiant population in the Perseus arm
  We present a new catalogue of cool supergiants in a section of the Perseus
arm, most of which had not been previously identified. To generate it, we have
used a set of well-defined photometric criteria to select a large number of
candidates (637) that were later observed at intermediate resolution in the the
Infrared Calcium Triplet spectral range, using a long-slit spectrograph. To
separate red supergiants from luminous red giants, we used a statistical
method, developed in previous works and improved in the present paper. We
present a method to assign probabilities of being a red supergiant to a given
spectrum and use the properties of a population to generate clean samples,
without contamination from lower-luminosity stars. We compare our
identification with a classification done using classical criteria and discuss
their respective efficiencies and contaminations as identification methods. We
confirm that our method is as efficient at finding supergiants as the best
classical methods, but with a far lower contamination by red giants than any
other method. The result is a catalogue with 197 cool supergiants, 191 of which
did not appear in previous lists of red supergiants. This is the largest
coherent catalogue of cool supergiants in the Galaxy.
