Metallicity Evolution of the Six Most Luminous M31 Dwarf Satellites
  We present global metallicity properties, metallicity distribution functions
(MDFs) and radial metallicity profiles for the six most luminous M31 dwarf
galaxy satellites: M32, NGC 205, NGC 185, NGC 147, Andromeda VII, and Andromeda
II. The results presented are the first spectroscopic MDFs for dwarf systems
surrounding a host galaxy other than the Milky Way. Our sample consists of
individual metallicity measurements for 1243 red giant branch (RGB) member
stars spread across these six systems. We determine metallicities based on the
strength of the Ca II triplet lines using the empirical calibration of Carrera
et al.(2013) which is calibrated over the metallicity range -4 < [Fe/H] <+0.5.
We find that these M31 satellites lie on the same luminosity-metallicity
relationship as the Milky Way dwarf satellites. We do not find a trend between
the internal metallicity spread and galaxy luminosity, contrary to previous
studies. The MDF widths of And II and And VII are similar to the MW dwarfs of
comparable luminosity, however, our four brightest M31 dwarf are more luminous
than any of the MW dwarf spheroidals and have broader MDFs. The MDFs of our six
M31 dwarfs are consistent with the leaky box model of chemical evolution,
although our metallicity errors allow a wide range of evolution models. We find
a significant radial gradient in metallicity in only two of our six systems,
NGC 185 and Andromeda II, and flat radial metallicity gradients in the rest of
our sample with no observed correlation between rotational support and radial
metallicity gradients. While the average properties and radial trends of the
M31 dwarf galaxies agree with MW counterparts at similar luminosity, the
detailed MDFs are different, particularly at the metal-rich end.
