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

Abstract

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