M giants with IGRINS: Detailed exploration of the M giants near-infrared spectra to chemically characterise the inner Milky Way

Abstract

Near-infrared spectroscopic observations are necessary in the chemo-dynamic exploration of the dust-ridden regions of the inner Milky Way (IMW) since high dust extinction prevents optical studies. Additionally, the stellar probes used for the chemical investigation of the IMW need to be bright. M giants are the best candidates for this since they are brighter but cooler ( T _eff < 4000 K). Due to large uncertainties in photometric methods, a method to determine the stellar parameters for M giants from the near-infrared spectra themselves is needed. Such a method would thus open up the possibility to analyse IMW regions. Furthermore, there are several unexplored absorption lines of various chemical species in the near-infrared spectra, but a reliable linelist is lacking. In a few papers, we presented a novel method determining stellar parameters for M giants using high-resolution IGRINS spectra and determined abundances of 21 elements using a well-tested HK-band linelist.