Near-infrared spectroscopic indices for unresolved stellar populations

I. Template galaxy spectra^⋆,⋆⋆

¹ GEPI, Observatoire de Paris, PSL Research University, CNRS, Univ. Paris Diderot, Sorbonne Paris Cité, 61 Avenue de l’Observatoire, 75014 Paris, France
e-mail: patrick.francois@obspm.fr
² Instituto de Astronomìa y Ciencias Planetarias Universidad de Atacama, Copiapò, Chile
³ Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
⁴ INAF-Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁵ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
⁶ European Southern Observatory, Ave. Alonso de Córdova 3107, Vitacura, Santiago, Chile

Received: 26 July 2018
Accepted: 8 October 2018

Abstract

Context. A new generation of spectral synthesis models has been developed in recent years, but there is no matching set of template galaxy spectra, in terms of quality and resolution, for testing and refining the new models.

Aims. 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.

Methods. 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.

Results. X-shooter spectra spanning the optical and infrared wavelengths (350–2400 nm) of bright nearby elliptical galaxies with a resolving power of R ∼ 4000–5400 were obtained. Heliocentric systemic velocity, velocity dispersion, and Mg, Fe, and Hβ line-strength indices are presented.

Conclusions. We present a library of very-high-quality spectra of galaxies covering a large range of age, metallicity, and morphological type. Such a dataset of spectra will be crucial to addressing important questions of the modern investigation concerning galaxy formation and evolution.