Govind Nandakumar (Lund University): M giants with IGRINS: Detailed exploration of the M giants near infrared spectra to chemically characterise the inner Milky Way

Thursday 26 Sept 2024, 14:00 → 15:00 Europe/Stockholm

Title: M giants with IGRINS: Detailed exploration of the M giants near infrared spectra to chemically characterise the inner Milky Way
Speaker: Govind Nandakumar
Affiliation: Lund University
Time: Thursday 26th September 2024, 14:00 to 15:00
Location: 101136B Å

Abstract: Near infrared spectroscopic observations are necessary in the chemo dynamic exploration of the dust-ridden regions of the inner Milky Way (IMW), where most of the Milky Way mass lies, 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 (Teff < 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 efficiently allow IMW regions to be analysed. Furthermore, there are several unexplored absorption lines of various chemical species in the near infrared spectra, but a reliable linelist is lacking.

In this talk, I will introduce a novel method to estimate stellar parameters of M giants using high resolution (R~45000) HK-band (1.4-2.4 um) IGRINS spectra. I will present the testing and validation of this method using nearby M giants with interferometric measurements and in APOGEE catalog. I will also show the elemental abundance trends versus metallicity for upto 22 elements determined for solar neighbourhood M giants using our well tested HK band linelist. Further, I will present the preliminary results from the application of this method to determine stellar parameters and elemental abundances for seven M giants in the inner Galactic bulge and 20 M giants in the NSC. Lastly, I will compare the IMW abundance trends versus metallicity with those from solar neighbourhood stars observed with the same instrument and analysed in the same manner using the same linelist to investigate the similarities/differences in IMW stars compared to those in the solar neighbourhood.