Optical and near-infrared colours as a discriminant of the age and metallicity of stellar populations

Carter, David and Smith, Daniel J. B. and Percival, Susan M. and Baldry, Ivan K. and Collins, Christopher A. and James, Philip A. and Salaris, Maurizio and Simpson, Chris and Stott, John P. and Mobasher, Bahram (2009) Optical and near-infrared colours as a discriminant of the age and metallicity of stellar populations. Monthly Notices of the Royal Astronomical Society, 397 (2). pp. 695-708. ISSN 0035-8711

Abstract

We present a comprehensive analysis of the ability of current stellar population models to reproduce the optical (ugriz) and near-infrared (JHK) colours of a small sample of well-studied nearby elliptical and S0 galaxies. We find broad agreement between the ages and metallicities derived using different population models, although different models show different systematic deviations from the measured broad-band fluxes. Although it is possible to constrain simple stellar population models to a well-defined area in age-metallicity space, there is a clear degeneracy between these parameters even with such a full range of precise colours. The precision to which age and metallicity can be determined independently, using only broad-band photometry with realistic errors, is Δ[Fe/H] ≃ 0.18 and Δlog Age ≃ 0.25. To constrain the populations and therefore the star formation history further, it will be necessary to combine broad-band optical-IR photometry with either spectral line indices, or else photometry at wavelengths outside this range.