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

Universidade Federal do Rio Grande do Sul, Instituto de Física, CP  15051, Porto Alegre CEP 91501-970, RS, Brazil

Corresponding author: Ch. Bonatto, charles@if.ufrgs.br

Received: 11 March 2003
Accepted: 2 July 2003

Abstract

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 – , , , , , and older than 10¹⁰ years, and metallicity in the range . This study employs two-dimensional STIS spectra in the range 2900–5700 Å, 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 λ5870 Å  flux and mass fraction, comes from old stars (age  years). We verified the possible existence of circumnuclear bursts (CNBs) in NGC 3115 and NGC 4203.