Empirical calibration of the near-infrared CaII triplet - I. The stellar library and index definition

This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2001 RAS. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. We thank Guy Worthey for providing us with a list of candidate stars at the beginning of this project. Ayvur Peletier’s help is acknowledged with the observations and the web page design. AJC acknowledges the hospitality of the Department of Physics (University of Durham) and the School of Physics and Astronomy (University of Nottingham). We also thank S. Pedraz and A. Gil de Paz for helpful suggestions. 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 für Astronomie, Heidelberg, and the Spanish Comisión Nacional de Astronomía. This research has made use of the Simbad data base (operated at CDS, Strasbourg, France), the NASAs Astrophysics Data System Article Service, and the Hipparcos Input Catalogue. AJC acknowledges the Comunidad de Madrid for a Formación de Personal Investigador fellowship. AV acknowledges the support of the PPARC rolling grant ‘Extragalactic Astronomy and Cosmology in Durham 1998-2002’ and of a British Council grant within the British/Spanish Joint Research Programme (Acciones Integradas). This work was supported by the Spanish Programa Sectorial de Promoción del Conocimiento under grant No. PB96-610.
A new stellar library at the near-IR spectral region developed for the empirical calibration of the Ca II triplet and stellar population synthesis modelling is presented. The library covers the range lambda lambda 8348-9020 at 1.5-Angstrom (FWHM) spectral resolution, and consists of 706 stars spanning a wide range in atmospheric parameters. We have defined a new set of near-IR indices, CaT*, CaT and PaT, which mostly overcome the limitations of previous definitions, the former being specially suited for the measurement of the Ca II triplet strength corrected for the contamination from Paschen lines. We also present a comparative study of the new and the previous Ca indices, as well as the corresponding transformations between the different systems. A thorough analysis of the sources of index errors and the procedure to calculate them is given. Finally, index and error measurements for the whole stellar library are provided together with the final spectra.
PPARC rolling grant ‘Extragalactic Astronomy and Cosmology
British Council
British/Spanish Joint Research Programme (Acciones Integradas)
Spanish Programa Sectorial de Promoción del Conocimiento
Depto. de Física de la Tierra y Astrofísica
Fac. de Ciencias Físicas
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