Abstract
We present a probabilistic formulation of the classical problem of synthesizing spectral properties of a galaxy using a base of star clusters. The problem consists of estimating the population vector x, composed by the contributions of n_star base elements to the integrated spectrum of a galaxy, and the extinction A_V, given a set of absorption line equivalent widths and continuum colors. The formalism is applied to the n_star = 12 base defined by Schmidt etal and subsequently used in several studies. The 13-D parameter space is explored with a Markov chain Monte Carlo sampling scheme based on the Metropolis algorithm, which produces a smooth and efficient mapping of the P(x,A_V) probability distribution. This version of Empirical Population Synthesis is used to investigate the ability to recover the detailed history of star-formation and chemical evolution using this spectral base. This is studied as a function of (1) the magnitude of the measurement errors and (2) the set of observables used in the synthesis. Only for extremely high S/N all 12 base proportions can be accurately recovered, though the observables are very precisely reproduced for any S/N. Furthermore, the individual mean x components are biased in the sense that components which carry a large fraction of the light tend to share their contribution preferably among components of same age. This compensation effect is linked to noise-induced linear dependences in the base, which very effectively redistribute the likelihood in x-space. The age distribution, however, can be satisfactorily recovered for realistic data quality. (abridged)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.