Stellar population gradient in lenticular galaxies: NGC 1023, NGC 3115 and NGC 4203

We investigate the stellar population content in the lenticular galaxies NGC1023, NGC3115 and NGC 4203 applying a population synthesis method based on a seven component spectral basis with different ages - 2.5 x 10(6), 10 x 10(6), 25 x 10(6), 75 x 10(6), 200 x 10(6), 1,2 x 10(9) and older than 10(10) years, and metallicity in the range - 1.3 less than or equal to [Z/Z(.)] less than or equal to - 0.2. This study employs two-dimensional STIS spectra in the range lambdalambda2900 - 5700 Angstrom, obtained from the Hubble Space Telescope public archives. We extracted one-dimensional spectra in adjacent windows 100 pc wide ( projected distance) from the nuclear regions up to 300 - 400 pc. The largest contribution, both in lambda5870Angstrom flux and mass fraction, comes from old stars (age > 10(10) years). We verified the possible existence of circumnuclear bursts (CNBs) in NGC3115 and NGC4203.