How well can we determine ages and chemical abundances from spectral fitting of integrated light spectra?

TL;DR

This study investigates how the choice of wavelength range affects the accuracy of determining ages and chemical abundances from integrated light spectra of globular clusters, highlighting optimal spectral regions for each parameter.

Contribution

It systematically evaluates the impact of spectral range selection on parameter inference, providing guidelines for improved spectral fitting techniques.

Findings

Parameter estimates vary with wavelength range used.

Wider spectral ranges improve reddening estimates.

Optimal spectral regions identified for age, [Fe/H], and [alpha/Fe].

Abstract

The pixel-to-pixel spectral fitting technique is often used in studies of stellar populations. It enables the user to infer several parameters from integrated light spectra such as ages and chemical abundances. In this paper, we examine the question of how the inferred parameters change with the choice of wavelength range used. We have employed two different libraries of integrated light spectra of globular clusters (GCs) from the literature and fitted them to stellar population models using the code Starlight. We performed tests using different regions of the spectra to infer reddening, ages, [Fe/H] and [alpha/Fe]. Comparing our results to age values obtained from isochrone fitting and chemical abundances from high resolution spectroscopy, we find that: (1) The inferred parameters change with the wavelength range used; (2) The method in general retrieves good reddening estimates, specially when a wider wavelength range is fitted; (3) The ideal spectral regions for determination of age, [Fe/H], and [alpha/Fe] are: 4170-5540A, 5280-7020A, and 4828-5364A, respectively; (4) The retrieved age values for old metal-poor objects can be several Gyr younger than those resulting from isochrone fitting. We conclude that, depending on the parameter of interest and the accuracy requirements, fitting the largest possible wavelength range may not necessarily be the best strategy.