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

We investigate the stellar population content in the lenticular galaxies NGC 1023, NGC 3115 and NGC 4203 applying a population synthesis method based on a seven component spectral basis with different ages – 2.5 * 10^(6), 10 * 10^(6), 25 * 10^(6), 75 *10^(6) , 200 * 10^(6), 1.2 * 10^(9) and older than 1010 years, and metallicity in the range -1.3 <=[Z/Z(circled dot operator)]<= -0.2. This study employs two-dimensional STIS spectra in the range (lambda)(lambda)2900-5700 A, obtained from the Hubble Space Telescope public archives. We extracted onedimensional spectra in adjacent windows 100 pc wide (projected distance) from the nuclear regions up to 300-400 pc. The largest contribution, both in (lambda)5870 A flux and mass fraction, comes from old stars (age >10^10 years). We verified the possible existence of circumnuclear bursts (CNBs) in NGC 3115 and NGC 4203.