Galaxy formation and evolution: low-surface-brightness galaxies |
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| Authors: | Raul Jimenez Paolo Padoan Francesca Matteucci & Alan F Heavens |
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| Institution: | Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ,;Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 216, 72000 Puebla, México,;Department of Astronomy, University of Trieste, SISSA/ISAS, Via Beirut 2-4, 34014 Trieste, Italy |
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| Abstract: | We investigate in detail the hypothesis that low-surface-brightness galaxies (LSBs) differ from ordinary galaxies simply because they form in haloes with large spin parameters. We compute star formation rates using the Schmidt law, assuming the same gas infall dependence on surface density as used in models of the Milky Way. We build stellar population models, predicting colours, spectra and chemical abundances. We compare our predictions with observed values of metallicity and colours for LSBs, and find excellent agreement with all observables. In particular, integrated colours, colour gradients, surface brightness and metallicity match very well to the observed values of LSBs for models with ages larger than 7 Gyr and high values (λ > 0.05) for the spin parameter of the haloes. We also compute the global star formation rate (SFR) in the Universe due to LSBs, and show that it has a flatter evolution with redshift than the corresponding SFR for normal discs. We furthermore compare the evolution in redshift of Zn / H ] for our models to those observed in damped Lyman α systems by Pettini et al. and show that damped Lyman α system abundances are consistent with the predicted abundances at different radii for LSBs. Finally, we show how the required late redshift of collapse of the halo may constrain the power spectrum of fluctuations. |
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| Keywords: | galaxies: evolution galaxies: formation galaxies: spiral galaxies: stellar content |
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