Abstract
Until recently, the potential of the near-infrared (NIR) spectral range for interpreting the stellar populations of elliptical galaxies (Es) was still almost unexploited. Previous calibrations of NIR line-strength indices suffer from limitations that translate into severe uncertainties on the predictions of stellar population synthesis models. In order to overcome the above problems, in this thesis we have calibrated new line-strength indices on the basis of a new, extensive NIR stellar library that consists of 706 spectra (ll8348–9020; FWHM p 1.50 A) with a wide range of atmospheric parameters. The new indices have been designed to measure the Ca ii triplet at ll8498, 8542, 8662, the H Paschen series, the Mg i line at l8807, and the TiO bands. Unlike previous definitions, they exhibit reliable pseudocontinua for all spectral types, and the Ca ii index has been corrected for the contamination with Paschen lines in early spectral types. The large sample of spectra, as well as the wide range of atmospheric parameters, allowed us to compute accurate empirical fitting functions for the indices. These, together with the stellar spectra, have been implemented into a recent single stellar population (SSP) synthesis model, concluding that, for SSPs older than 3 Gyr, (1) the age is a secondary parameter, (2) the Ca ii indices of SSPs with intermediate to high metallicity mainly depend on the initial mass function (IMF) slope (m; assuming a Salpeter-like IMF) in the sense that they decrease with increasing m, and (3) the TiO index is an excellent metallicity indicator. The inclusion of M-type stars in our stellar library reveals unprecedented behaviors for metal-rich SSPs, such as the saturation—or even a decreasing trend—of the integrated Ca ii with increasing metallicity. Finally, new spectroscopic data for a sample of 35 Es are interpreted in the light of our model predictions. The most surprising result is the significant anticorrelation between the
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Publications of the Astronomical Society of the Pacific
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
