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Evolution des galaxies dans les domaines X et optique. Histoire de la formation d'étoiles et de la métallicité.

Abstract : We present an attempt to link consistently the spectral energy distributions of evolved galaxies in X-rays and in the optical. New X-ray observatories in orbit (XMM et CHANDRA) as well as large ground-based telescopes (VLT) can now observe near and distant galaxies with a high precision. The study of X-ray sources in galaxies enhances the major role played by dying stars. Supernovae remnants, high mass X-ray binaries and low-mass X-ray binaries are probably the most frequent and the most luminous ones. Some hot gas is also present in star forming regions and in elliptical galaxies. The absorption by the cold interstellar medium is often very strong below 1 keV. By associating the modeled spectra of theses sources and a code of evolutionary spectral synthesis, we can predict the X-ray spectra of galaxies, which may have various star formation histories. We extend the spectral covering of the energy distributions computed until now from the ultraviolet to the near infrared. The strength of this coupling is its ability to predict consistently the formation of stars (which appears mainly in the optical spectra), and their deaths (the remnants being often strong X-ray sources). Moreover, the metallicities of the stars and of the interstellar medium evolve as the stars die, and show various features at every wavelength. We present the predicted spectra and X-ray colors of synthetic galaxies of every spectral type. We explain the correlations observed between the star formation rates, the B-band luminosities and the X-ray luminosities. Then, we apply our models to the prediction of X-ray luminosity functions for normal galaxies. Using these results, we provide an estimation of the contribution of normal galaxies to the X-ray background. Moreover, the study of the star formation history and of the evolution of metallicity is also done in the optical. We make a code of inverse spectral synthesis and we apply it to local elliptical galaxies. We also use an extension of this code to compute photometric redshifts and to analyse the star formation histories of distant galaxies. Finally, we propose a study of the stellar absorption lines in the optical light of galaxies, by linking the code of spectrophotometric evolution PÉGASE to a new high resolution spectral library. Then, we define two new spectra indices characterizing well the ages and the metallicities of stellar populations.
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  • HAL Id : tel-00455432, version 1

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Damien Le Borgne. Evolution des galaxies dans les domaines X et optique. Histoire de la formation d'étoiles et de la métallicité.. Astrophysique [astro-ph]. Université Paris Sud - Paris XI, 2003. Français. ⟨tel-00455432⟩

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