Identification of Absorption Lines of Heavy Metals in the Wavelength Range 0.97--1.32 Micron

TL;DR

This study identifies and confirms heavy metal absorption lines in the near-infrared spectrum of stars, providing new diagnostic tools for studying galactic chemical evolution despite limited line numbers.

Contribution

The paper presents the first identification of heavy metal absorption lines in the 0.97--1.32 micron range using synthetic spectra and stellar observations, expanding infrared spectral diagnostics.

Findings

Detected lines of Zn I, Sr II, Y II, Zr I, Ba II, Sm II, Eu II, Dy II.

Confirmed presence of lines not predicted by synthetic spectra.

Provided potential diagnostic lines for galactic chemical evolution.

Abstract

Stellar absorption lines of heavy elements can give us various insights into the chemical evolution of the Galaxy and nearby galaxies. Recently developed spectrographs for the near-infrared wavelengths are becoming more and more powerful for producing a large number of high-quality spectra, but identification and characterization of the absorption lines in the infrared range remain to be fulfilled. We searched for lines of the elements heavier than the iron group, i.e., those heavier than Ni, in the Y (9760--11100 AA) and J (11600--13200 AA) bands. We considered the lines in three catalogs, i.e., Vienna Atomic Line Database (VALD), the compilation by R. Kurucz, and the list published in 1999 by Melendez and Barbuy. Candidate lines were selected based on synthetic spectra and the confirmation was done by using WINERED spectra of 13 supergiants and giants within FGK spectral types (spanning 4000--7200 K in the effective temperature). We have detected lines of Zn I, Sr II, Y II, Zr I, Ba II, Sm II, Eu II, and Dy II, in the order of atomic number. Although the number of the lines is small, 23 in total, they are potentially useful diagnostic lines of the Galactic chemical evolution, especially in the regions for which interstellar extinction hampers detailed chemical analyses with spectra in shorter wavelengths. We also report the detection of lines whose presence was not predicted by the synthetic spectra created with the above three line lists.