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Abstract: Aims. We provide an easy-to-use full-spectrum fitting package and explore itsapplications to i the determination of the stellar atmospheric parameters andii the study of the history of stellar populations. Methods. We developedULySS, a package to fit spectroscopic observations against a linear combinationof non-linear model components convolved with a parametric line-of-sightvelocity distribution. The minimization can be either local or global, anddetermines all the parameters in a single fit. We use chi2 maps, convergencemaps and Monte-Carlo simulations to study the degeneracies, local minima and toestimate the errors. Results. We show the importance of determining the shapeof the continuum simultaneously to the other parameters by including amultiplicative polynomial in the model without prior pseudo-continuumdetermination, or rectification of the spectrum. We also stress the beneficeof using an accurate line-spread function, depending on the wavelength, so thatthe line-shape of the models properly match the observation. For simple models,i. e., to measure the atmospheric parameters or the age-metallicity of asingle-age stellar population, there is often a unique minimum, or when localminima exist they can unambiguously be recognized. For more complex models,Monte-Carlo simulations are required to assess the validity of the solution.Conclusions. The ULySS package is public, simple to use and flexible. The fullspectrum fitting makes optimal usage of the signal.



Author: Mina Koleva, Philippe Prugniel, Antoine Bouchard, Yue Wu

Source: https://arxiv.org/







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