  We provide here the documentation of the new version of the spectral
evolution model PEGASE. PEGASE computes synthetic spectra of galaxies in the UV
to near-IR range from 0 to 20 Gyr, for a given stellar IMF and evolutionary
scenario (star formation law, infall, galactic winds). The radiation emitted by
stars from the main sequence to the pre-supernova or white dwarf stage is
calculated, as well as the extinction by dust. A simple modeling of the nebular
emission (continuum and lines) is also proposed. PEGASE may be used to model
starbursts as well as old galaxies. The main improvements of PEGASE.2 relative
to PEGASE.1 (Fioc & Rocca-Volmerange 1997) are the following: (1)The stellar
evolutionary tracks of the Padova group for metallicities between 0.0001 and
0.1 have been included; (2)The evolution of the metallicity of the interstellar
medium (ISM) due to SNII, SNIa and AGB stars is followed. Stars are formed with
the same metallicity as the ISM (instead of a solar metallicity in PEGASE.1),
providing thus a metallicity-consistent model; (3)Lejeune et al.'s library of
stellar spectra is used; (4)The extinction by dust is computed for geometries
corresponding to disk and spheroidal galaxies using a radiative transfer code
taking into account the scattering. The main outputs (as a function of time)
are spectra, colors and magnitudes in various photometric systems,
luminosities, type II and Ia supernovae rates, line intensities and equivalent
widths, amount and metallicity of stars and gas, mass locked in stellar
remnants, optical depth and total dust emission. The corresponding article
(Fioc & Rocca-Volmerange 2000) will be submitted soon. A detailed modeling of
the spectrum of the dust emission and of HII regions (Moy, Rocca-Volmerange &
Fioc 2000) will be included in future versions.
