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Astron. Astrophys. 326, 950-962 (1997)

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PEGASE: a UV to NIR spectral evolution model of galaxies

Application to the calibration of bright galaxy counts

Michel Fioc 1 and Brigitte Rocca-Volmerange 1, 2

1 Institut d'Astrophysique de Paris, CNRS, 98 bis Bd. Arago, F-75014 Paris, France
2 Institut d'Astrophysique Spatiale, Bât. 121, Université Paris XI, F-91405 Orsay, France

Received 8 October 1996 / Accepted 22 May 1997


PEGASE (P rojet d'E tude des GA laxies par S ynthèse E volutive, in French) is a new spectrophotometric evolution model for starbursts and evolved galaxies of the Hubble sequence. Its main originality is the extension to the near-infrared (NIR) of the atlas of synthetic spectra of Rocca-Volmerange & Guiderdoni (1988) with a revised stellar library including cold star parameters and stellar tracks extended to the thermally-pulsing regime of the asymptotic giant branch (TP-AGB) and the post-AGB (PAGB) phase. The NIR is coherently linked to the visible and the ultraviolet (UV), so that the model is continuous on an exceptionally large wavelength range from 220 Å up to 5 µm. Moreover, a precise algorithm allows to follow very rapid evolutionary phases such as red supergiants or AGB crucial in the NIR. The nebular component is also computed in the NIR. The extinction correction is gas-dependent for spirals and ellipticals. A set of reference synthetic spectra at [FORMULA], to which apply cosmological k- and evolution e- corrections for high-redshift galaxies, is built from fits of observational templates. Because of the lack of visible to NIR spectral templates for each Hubble type, we adopt statistical samples of colors, not fitted by previous models.

A first application of this continuous model is to solve the problem of the slope of the bright galaxy counts from [FORMULA] to 19 and of the normalization parameter [FORMULA] of the Schechter luminosity function.

Designed to be used currently and to take into account easily new observational and theoretical inputs, the model is built as a series of independent blocks. Any block is clearly identified and submitted to publication. Code sources, input and output data are available 1 by anonymous ftp at ftp.iap.fr in /pub/from_users/pegase/ or at the WEB address of the authors: http://www.iap.fr/users/.

Key words: galaxies: evolution – infrared: galaxies – dust, extinction – galaxies: stellar content – cosmology: miscellaneous – galaxies: fundamental parameters

Send offprint requests to: M. Fioc (fioc@iap.fr)


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© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998