Abundances in eight bulge stars from the optical and near-infrared

TL;DR

This study compares stellar parameters and elemental abundances derived from optical and near-infrared spectra of bulge stars, highlighting the most suitable wavelength regions and challenges in spectral analysis for future large-scale observations.

Contribution

It provides a detailed comparison of optical and H-band spectroscopic analyses of bulge stars, identifying optimal lines and discussing challenges in stellar parameter determination.

Findings

Identified the most suitable wavelength regions for each element.

Highlighted difficulties in deriving stellar parameters in optical and H-band.

Emphasized the potential of near-infrared observations with upcoming instruments.

Abstract

Context: The abundances of the $\alpha$-elements are key for understanding the early chemical enrichment of the Galactic bulge. The elements of interest present lines in different wavelength regions, and some of them show lines only in part of the spectra. In the present work, the CNO trio, the alpha-elements Mg, Si, Ca, and Ti, and odd-Z Na and Al are examined as measured from optical and H-band lines. Aims: The aim of this work is to carry out a detailed comparison of stellar parameters and abundances derived in the optical and near-infrared (H-band). We also inspect the best available lines for a list of bulge stars previously analyzed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) team in the H-band and by our group in the optical. This work is mainly of interest to spectroscopists. Methods: In the present work, we compared the stellar parameters and abundance results derived from APOGEE H-band spectra with optical analyses based on Ultraviolet and Visual Echelle Spectrograph at the Very Large Telescope (VLT/UVES) data for eight bulge stars. Results:We point out the most suitable wavelength region for each of the studied elements, and highlight difficulties in the derivation of stellar parameters both in the optical and H-band. The near-infrared will allow observations of a large number of stars in the near future given new instruments soon to be available. The identification of spectral lines in this spectral region and the investigation of their reliability are ongoing efforts worldwide. New instruments will also allow simultaneous observation of H-band and optical.