  We present a study of the stellar population in Low Luminosity AGN (LLAGN).
Our goal is to search for spectroscopic signatures of young and intermediate
age stars, and to investigate their relationship with the ionization mechanism
in LLAGN. The method used is based on the stellar population synthesis of the
optical continuum of the innermost (20-100 pc) regions in these galaxies. For
this purpose, we have collected high spatial resolution optical (2900-5700 A)
STIS spectra of 28 nearby LLAGN that are available in the Hubble Space
Telescope archive. The analysis of these data is compared with a similar
analysis also presented here for 51 ground-based spectra of LLAGN. Our main
findings are: (1) No features due to Wolf-Rayet stars were convincingly
detected in the STIS spectra. (2) Young stars contribute very little to the
optical continuum in the ground-based aperture. However, the fraction of light
provided by these stars is higher than 10% in most of the weak-[OI] LLAGN STIS
spectra. (3) Intermediate age stars contribute significantly to the optical
continuum of these nuclei. This population is more frequent in objects with
weak than with strong [OI]. Weak-[OI] LLAGN that have young stars stand out for
their intermediate age population. (4) Most of the strong-[OI] LLAGN have
predominantly old stellar population. A few of these objects also show a
feature-less continuum that contributes significantly to the optical continuum.
These results suggest that young and intermediate age stars do not play a
significant role in the ionization of LLAGN with strong [OI]. However, the
ionization in weak-[OI] LLAGN with young and/or intermediate age population
could be due to stellar processes.
