Empirical calibration of the near-IR Ca II triplet - III. Fitting functions

Abstract

Using a near-IR stellar library of 706 stars with a wide coverage of atmospheric parameters, we study the behaviour of the Ca II triplet strength in terms of effective temperature, surface gravity and metallicity. Empirical fitting functions for recently defined line-strength indices, namely CaT*, CaT and PaT, are provided. These functions can be easily implemented into stellar populations models to provide accurate predictions for integrated Ca II strengths. We also present a thorough study of the various error sources and their relation to the residuals of the derived fitting functions. Finally, the derived functional forms and the behaviour of the predicted Ca II are compared with those of previous works in the field.

17 pages, 12 figures (two of them in colour), LaTeX. For associated software, see http://www.ucm.es/info/Astrof/ellipt/CATRIPLET.html or http://www.nottingham.ac.uk/~ppzrfp/CATRIPLET.html

References in corpus (4)

• Empirical calibration of the near-IR Ca II triplet - I. The stellar library and index definition
• Empirical calibration of the near-IR Ca II triplet - II. The stellar atmospheric parameters
• Empirical calibration of the λ4000 Åbreak
• Near-infrared Spectral Features in Single-aged Stellar Populations

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