Spatially resolved near-infrared spectroscopic indices for the massive elliptical galaxy IC 4296

¹ Instituto de Astronomía y Ciencias Planetarias, Universidad de Atacama, Copayapu 485, Copiapó, Chile
² Departamento de Astronomía, Universidad de La Serena, Av. Raúl Bitrán, 1305 La Serena, Chile
³ European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München, Germany
⁴ European Southern Observatory, Avenida Alonso de Córdova 3107, Vitacura, Santiago, Chile
⁵ Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova, vicolo dell’Osservatorio 3, I-35122 Padova, Italy
⁶ INAF-Osservatorio Astronomico di Padova, vicolo dell’Osservatorio 5, I-35122 Padova, Italy
⁷ Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
⁸ GEPI, Observatoire de Paris, PSL Research University, CNRS, Université Paris Diderot, Sorbonne Paris Cité, 61 Avenue de l’Observatoire, F-75014 Paris, France
⁹ Instituto de Astrofísica de Canarias, Calle Vía Láctea s/n, E-38200 La Laguna, Spain
¹⁰ Departamento de Astrofísica, Universidad de La Laguna, Calle Astrofísico Francisco Sánchez, E-38205 La Laguna, Spain
¹¹ Millennium Institute of Astrophysics, Nuncio Monsenor Sotero Sanz 100, Of. 104, Providencia, Santiago, Chile

^⋆ Corresponding author: daniele.gasparri@postgrados.uda.cl

Received: 17 October 2024
Accepted: 5 July 2025

Abstract

Context. In the near-infrared (NIR) region, a large number of absorption features may be used to constrain the properties of unresolved stellar populations of galaxies.

Aims. We present the results of a pilot project assessing the feasibility of measuring the distribution and radial trends of NIR line-strength indices on spatially resolved spectra. We used the ESO/KMOS multi-object spectrograph to observe the massive, nearby elliptical galaxy IC 4296.

Methods. We analysed the distribution of the NIR line-strength indices that are most sensitive to the age and metallicity of the galaxy stellar populations both on 2D maps and on stacked spectra of five radial bins. This allowed us to build the radial profiles of the line-strength indices out to 0.80 R_e and compare them to those measured in the optical range.

Results. For the particular case of IC 4296, we find that the metal indices have negative radial trends. The results are in agreement with literature radial profiles obtained from the analysis of the optical Lick/IDS indices and favour in situ galaxy formation over multiple merging events.

Conclusions. The obtained results demonstrate the usefulness of the NIR wavelength domain to unveil the processes of galaxy formation and evolution.