The Star-Forming Histories of the Nucleus, Bulge, and Inner Disk of NGC
  5102: Clues to the Evolution of a Nearby Lenticular Galaxy
  Long slit spectra recorded with GMOS on Gemini South are used to examine the
star-forming history of the lenticular galaxy NGC 5102. Structural and
supplemental photometric information are obtained from archival Spitzer [3.6]
images. Comparisons with model spectra point to luminosity-weighted
metallicities that are consistent with the colors of resolved red giant branch
stars in the disk. The nucleus has a luminosity-weighted age at visible
wavelengths of ~1 Gyr, and the integrated light is dominated by stars that
formed over a time period of only a few hundred Myr. For comparison, the
luminosity-weighted ages of the bulge and disk are ~2 Gyr and ~10 Gyr,
respectively. The g'-[3.6] colors of the nucleus and bulge are consistent with
the spectroscopically-based ages. In contrast to the nucleus, models that
assume star-forming activity spanning many Gyr provide a better match to the
spectra of the bulge and disk than simple stellar population models. Isophotes
in the bulge have a disky shape, hinting that the bulge was assembled from
material with significant rotational support. The star-forming histories of the
bulge and disk are consistent with the bulge forming from the collapse of a
long-lived bar, and it is suggested that the progenitor of NGC 5102 was a
barred disk galaxy that morphed into a lenticular galaxy through the buckling
of its bar.
