Near Infrared spectroscopic indices for unresolved stellar populations. I. Template galaxy spectra

TL;DR

This paper introduces a high-quality spectral library of nearby galaxies across the optical and infrared spectrum, providing essential templates for testing and refining spectral synthesis models of stellar populations.

Contribution

It presents a new library of high-resolution galaxy spectra spanning various types, ages, and metallicities, filling a gap for model validation in near-infrared spectral analysis.

Findings

Spectra cover 350-2400 nm with R~4000-5400 resolution.

Measured systemic velocities, velocity dispersions, and line indices.

Provides a baseline dataset for galaxy formation and evolution studies.

Abstract

A new generation of spectral synthesis models has been developed in the recent years, but there is no matching -- in terms of quality and resolution -- set of template galaxy spectra for testing and refining the new models. Our main goal is to find and calibrate new near-infrared spectral indices along the Hubble sequence of galaxies which will be used to obtain additional constraints to the population analysis based on medium resolution integrated spectra of galaxies. Spectra of previously studied and well understood galaxies with relatively simple stellar populations (e.g., ellipticals or bulge dominated galaxies) are needed to provide a baseline data set for spectral synthesis models. X-Shooter spectra spanning the optical and infrared wavelength (350-2400\,nm) of bright nearby elliptical galaxies with resolving power $ R\sim$4000-5400 were obtained. Heliocentric systemic velocity, velocity dispersion and Mg, Fe and \Hb\ line-strength indices are presented. We present a library of very high quality spectra of galaxies covering a large range of age, metallicity and morphological type. Such as a dataset of spectra will be crucial to address important questions of the modern investigation concerning galaxy formation and evolution.