Abstract. We present PEGASE-HR, a new stellar population synthesis program generating high resolution spectra (R = 10 000) over the optical range λλ = 400-680 nm. It links the spectro-photometric model of galaxy evolution PEGASE.2 (Fioc & Rocca-Volmerange 1997) to an updated version of the ELODIE library of stellar spectra observed with the 193 cm telescope at the Observatoire de Haute-Provence (Prugniel & Soubiran 2001a). The ELODIE star set gives a fairly complete coverage of the Hertzprung-Russell (HR) diagram and makes it possible to synthesize populations in the range [Fe/H] = −2 to +0.4. This code is an exceptional tool for exploring signatures of metallicity, age, and kinematics. We focus on a detailed study of the sensitivity to age and metallicity of the high-resolution stellar absorption lines and of the classical metallic indices proposed until now to solve the age-metallicity degeneracy. Validity tests on several stellar lines are performed by comparing our predictions for Lick indices to the models of other groups. The comparison with the lower resolution library BaSeL (Lejeune et al. 1997) confirms the quality of the ELODIE library when used for single stellar populations (SSPs) from 10 7 to 2 × 10 10 yr. Predictions for the evolved populations of globular clusters and elliptical galaxies are given and compared to observational data. Two new highresolution indices are proposed around the Hγ line. They should prove useful in the analysis of spectra from the new generation of telescopes and spectrographs.

Abstract. The narrow K-z relation of powerful radio galaxies in the Hubble K-band diagram is often attributed to the stellar populations of massive elliptical galaxies. Because it extends over a large range of redshifts (0 < z < 4), it is difficult to estimate masses at high redshifts by taking into account galaxy evolution. In the present paper, we propose to estimate the stellar masses of galaxies using the galaxy evolution model PÉGASE. We use star formation scenarios that successfully fit faint galaxy counts as well as z = 0 galaxy templates. These scenarios also predict spectra at higher z, used to estimate valid photometric redshifts. The baryonic mass of the initial gas cloud M bar is then derived. The K-z relation is remarkably reproduced by our evolutionary scenario for elliptical galaxies of baryonic mass M bar,max 1012 M , at all z up to z = 4. M bar,max is also the maximum mass limit of all types of galaxies. Using another initial mass function (IMF), even a top-heavy one, does not alter our conclusions. The high value of M bar,max observed at z > 4 implies that massive clouds were already formed at early epochs. We also find that the M bar,max limit is similar to the critical mass M crit of a self-gravitating cloud regulated by cooling (Rees & Ostriker 1977;Silk 1977). Moreover, the critical size r crit 75 kpc is remarkably close to the typical diameter of Lyα haloes surrounding distant radio galaxies. This confirms the validity of the method of baryonic mass determination based on the K-band luminosity. A puzzling question that remains to be answered is the short time-scale of mass-accumulation required to form such massive galaxies at z = 4. We discuss the dispersion of the K-z relation in terms of uncertainties on the mass limit. The link between the presence of the active nucleus and a large stellar mass is also discussed.

This paper represents a collective effort to provide an extensive electronic database useful for the interpretation of the spectra and evolution of galaxies. A broad variety of empirical and theoretical data are discussed here, and the data are made fully available in the AAS CD-ROM Series, Vo. 7. Several empirical stellar libraries are part of this database. They cover the ultraviolet spectral range observed with IUE, optical data from different ground-based telescopes, and ground-based infrared data. Spectral type coverage depends on the wavelength, but it is mostly complete for types O and M and luminosity classes V to I. A large metallicity range is covered as well. Theoretical libraries of selected spectral indices of cool stars and of stellar continuum fluxes in the temperature range 2000 K to 50,000 K, as well as Wolf-Rayet energy distributions are presented. Several libraries of star clusters and early-type galaxies have been selected for this database. We discuss an extensive set of empirical spectra templates covering the wavelength region from 1200 - 9800 A, as well as narrow-band line indices in a large number of passbands. Bench-mark spectra of nearby galaxies for model tests are included as well. We compiled numerous evolutionary models and isochrones for stars of all mass ranges of interest, wide metallicity range, and for all evolutionary phases, including the pre-main-sequence phase. The majority of the models have been computed by the Geneva and Padova groups. Evolutionary synthesis models computed by several independent groups are made available. They can be applied to old and young systems, and are optimized with respect to different aspects of input physics. The model predictions include stellar (colors, magnitudes, absorption features) and nebular (emission-line fluxes) properties. Finally, we present models of ionized gas to be used for the interpretation of active galactic nuclei and young star-forming galaxies. The community is encouraged to make use of this electronic database and to perform a critical comparison between the individual datasets

Abstract. We analyze coherently the stellar and nebular energy distributions of starbursts and H ii galaxies, using our evolutionary synthesis model, PÉGASE (Fioc & Rocca-Volmerange 1997, 2000, coupled to the photoionization code CLOUDY (Ferland 1996). The originality of this study is to relate the evolution and the metallicity of the starburst to the past star formation history of the host galaxy. Extinction and geometrical effects on emission lines and continua are computed in coherency with metallicity. We compare our model predictions to an observed sample of ≈ 750 H ii regions and starbursts.When/Hβ, the most striking feature is the decreasing spread in U with increasing metallicity Z. High-U objects systematically have a low metallicity while low levels of excitation happen at any Z. The best fits of emission line ratios are obtained with a combination of a high-and a low-ionization components. No additional source of ionizing photons -shocks or hidden AGN -is needed. The high level of excitation observed in metal-poor H ii galaxies requires a very young population (≤ 3 Myr), while starburst nuclear galaxies (SBNGs) are consistent with a wider range of age (≤ 5 Myr).Colors (B − V , V − R) and equivalent widths are fitted in coherency with emission line ratios. An underlying population is needed, even for small-aperture observations. This evolved population not only reddens the continuum and dilutes the equivalent width of the emission lines, but also participates in the ionization process. Its main effect on line ratios is to maintain a high level of excitation when the burst stops. Models combining underlying populations typical of Hubble sequence galaxies and instantaneous starbursts with ages between 0 and 8 Myr agree satisfactorily with all the data.