We show that different stellar mass estimation methods yield overall mass scales that disagree by factors up to ∼2 for the galaxy population and, more importantly, relative mass scales that sometimes disagree by z p 0 factors 3 between distinct classes of galaxies (spiral/irregular types, classical E/S0s, and E/S0s whose colors reflect recent star formation). This comparison considers stellar m...

Far-ultraviolet (900-1200Å) spectral synthesis of nine giant extragalactic H II regions in M33 and M101 is performed to study their massive stellar content. Several parameters are quantified, predicted, and compared to the literature: age, stellar mass, IMF slope, number of O-type and Wolf-Rayet stars, Hα and 5500Å continuum fluxes. The results of this particular technique are consistent with o...

Far-ultraviolet (900-1200Å) spectral synthesis of nine giant extragalactic H II regions in M33 and M101 is performed to study their massive stellar content. Several parameters are quantified, predicted, and compared to the literature: age, stellar mass, IMF slope, number of O-type and Wolf-Rayet stars, Hα and 5500Å continuum fluxes. The results of this particular technique are consistent with o...

The formation and evolution of elliptical galaxies (EGs) is still an open question. In particular, recent observations suggest that elliptical galaxies are not only simple spheroidal systems of old stars. In this paper we analyze a sample of elliptical galaxies selected from the Sloan Digital Sky Survey in order to study the star-forming activity in local elliptical galaxies. Among these 487 el...

We have observed the largest optical spectra sample of 74 blue compact galaxies. Stellar population properties of them were derived by comparing the equivalent widths of strong absorption features and continuum colors, using a method of empirical population synthesis based on star cluster sample. The results indicate that blue compact galaxies are typically age-composite stellar system, the con...

We investigate the stellar content of the starburst dwarf galaxy IC10 using accurate and deep optical data collected with the Advanced Camera for Surveys and with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. The comparison between theory and observations indicates a clear change in age distribution when moving from the center toward the external regions. Moreover, empi...

We study the old problem of the uniqueness of chemical evolution models. We showed in Mollá et al. (1999) that multiphase models for three Virgo cluster galaxies were able to reproduce the observed radial distributions of spectral indices Mg2 and Fe52. But those models may fit the present-epoch radial distributions with different star formation histories (Tosi 1996). The two spectral indices ab...

We present J-band (1.15 − 1.35μm) spectroscopy of a sample of nine galaxies showing some degree of LINER activity (classical LINERs, weak-[O i] LINERs and transition objects), together with H-band spectroscopy for some of them. A careful subtraction of the stellar continuum allows us to obtain reliable [Fe ii]1.2567μm/Paβ line ratios. We conclude that different types of LINERs (i.e., photoioniz...

Aims. We investigate the build-up of stellar mass through star formation in field galaxies, galaxy groups, and clusters in order to better understand the physical processes regulating star formation in different haloes. Methods. In order to do so we relate ongoing star formation activity to the stellar mass by studying the integrated specific star formation rate (SSFR), defined as the star-form...

We investigate the effects of abundance and age on the mid-UV spectra and Mg2 strengths of stellar populations using simple population synthesis models. These models are used to constrain the star formation history of four nearby elliptical galaxies and spiral bulges. The mid-UV (1800 3200 Å) light of evolved stellar populations (> 1 Gyr) is dominated by the main sequence turn-off, unlike the o...