Spatially resolved stellar population parameters in the BCGs of two
  fossil groups
  We report the results of Gemini/GMOS long-slit spectroscopic observations
along the major and minor axes of the central galaxies in two fossil groups,
SDSS J073422.21+265133.9 and SDSS J075828.11+374711.8 (the NGC 2484 group).
Spatially resolved kinematics and stellar population parameters (ages,
metallicities and $\alpha$-element abundance ratios) derived using ~20 Lick
indices are presented. Despite remarkable similarities in their morphologies,
photometric properties (luminosity and colour) and kinematics, the two galaxies
exhibit significantly different stellar population parameters.
  SDSS J073422.21+265133.9 exhibits a strong metallicity gradient
(Delta[Z/H]/Delta R ~ -0.4) all the way into the centre of the galaxy. It also
exhibits an age profile that suggest a relatively recent, centrally
concentrated burst of star formation superimposed on an older, more spatially
extended population. NGC 2484, a well known X-ray AGN, exhibits a flat
core-like structure in its metallicity gradient, but no detectable age
gradient. The alpha-element abundance ratio ([E/Fe]) profiles of the two
galaxies are also significantly different. SDSS J073422.21+265133.9 exhibits a
slightly positive gradient (Delta [E/H]/Delta R ~ 0.1), perhaps again
suggesting a more recent central burst of star formation, while NGC 2484 shows
a negative gradient (Delta [E/H]/Delta R ~-0.1), indicating that star formation
may have happened "inside out".
  Our analysis of these two galaxies of similar mass, morphology and kinematics
therefore suggests two different mechanisms to have been in action during their
formation. Consequently, we conclude that the central galaxies of fossil groups
can not be considered a homogeneous group with regard to their formation
processes or star formation histories.
