Using spectroscopic data to disentangle stellar population properties



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Cardiel López, Nicolás and Gorgas García, Francisco Javier and Sánchez Blázquez, P. and Cenarro, A. J. and Pedraz, S. and Bruzual, G. and Klement, J. (2003) Using spectroscopic data to disentangle stellar population properties. Astronomy and astrophysics, 409 (2). pp. 511-522. ISSN 0004-6361

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It is well known that, when analyzed in the light of current synthesis model predictions, variations in the physical properties of single stellar populations (e.g. age, metallicity, initial mass function, element abundance ratios) may have a similar effect in their integrated spectral energy distributions. The confusion is even worsened when more realistic scenarios, i.e. composite star formation histories, are considered. This is, in fact, one of the major problems when facing the study of stellar populations in star clusters and galaxies. Typically, the observational efforts have aimed to find the most appropriate spectroscopic indicators in order to avoid, as far as possible, degeneracies in the parameter space. However, from a practical point of view, the most suited observables are not, necessarily, those that provide more orthogonality in that parameter space, but those that give the best balance between parameter degeneracy and sensitivity to signal-to-noise ratio per Angstrom, S/N(Angstrom). In order to achieve the minimum combined total error in the derived physical parameters, this work discusses how the functional dependence of typical line-strength indices and colors on S/N(Angstrom) allows to define a suitability parameter which helps to obtain more realistic combinations of spectroscopic data. As an example, we discuss in more detail the problem of breaking the well known age-metallicity degeneracy in relatively old stellar populations, comparing the suitability of different spectroscopic diagrams for a simple stellar population of solar metallicity and of 12 Gyr in age.

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© ESO 2003. Valuable discussions with A. Vazdekis, and J. J. González are gratefully acknowledged. The data employed in Appendix A was obtained with the 1m JKT, 2.5m INT and the 4.2m WHT at La Palma Observatory, and with the 3.5m Telescope at Calar Alto Observatory. The JKT, INT and WHT are operated on the island of La Palma by the Royal Greenwich Observatory at the Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. The Calar Alto Observatory is operated jointly by the Max-Planck-Institute fur Astronomie, Heidelberg, and the Spanish Comisión Nacional de Astronomía. This work was supported by the Spanish Programa Nacional de Astronomía y Astrofísica under grant AYA2000-977.

Uncontrolled Keywords:Early-type galaxies; Evolutionary synthesis models; Infrared CAII triplet; Digital sky survey; France redshift survey; Line-strength indexes; Elliptic galaxies; Empirical calibration; Spectral evolution; Star-formation
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
Sciences > Physics > Atmospheric physics
ID Code:29658
Deposited On:20 Apr 2015 15:28
Last Modified:10 Dec 2018 15:05

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