Chemical abundances in metal-rich bulge field stars

• Grant number: 25/00600-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2025
• End date: March 31, 2026
• Field of knowledge: Physical Sciences and Mathematics - Astronomy - Stellar Astrophysics
• Principal Investigator: Beatriz Leonor Silveira Barbuy
• Grantee: Ana Luisa Rocha de Abreu
• Host Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 20/15245-2 - The multi-object spectrograph (MOSAIC) for the extremely large telescope: spectroscopy of stellar populations in the milky way and external galaxies, AP.ESP

Abstract

The Galactic bulge is the most complex region of the Galaxy, because it was the first structure to be formed, but after that other stellar populations occupy this region such as the thin and thick disksand halo, besides the formation of the bar that caused transfer of gas and stars from the disk to the inner Galaxy. Moreover, accretion of dwarf galaxies took place, of which stellar populations mixed with the original bulge.With the aim of studying the oldest and original bulge stars, that are distribution in a spheroid, we applied the following criteria: We selected stars from the Reduced Proper-Motion (RPM) sample from Queiroz et al. (2020, 2021). RPM is defined as H = m+5log mu = M+5logT, where m is apparent magnitude; mu = M+5logT, where m is apparent the total annual proper motion (in arc seconds per year); M the absolute magnitude; and T the transverse velocity (in a.u. per year). The RPM sample was then cross-matched with stars observed in the H-Band within the APOGEE survey, and appliedcriteria to find stars belonging to the early bulge, formed in the earliest phases of the Galaxyformation. In previous work we selected stars with metallicity [Fe/H] $<$ -0.8, and here we complement the study by selection stars with metallicity[Fe/H] $>$ -0.8. The criteria are: 1. Vphi < 0 to select stars "counter-rotating" relative to the bulge rotation,2. Not-bar following, 3. Metallicity [Fe/H] $>$ -0.8, 4. Apogalactic distance Apo $<$ 4 kpc,5. Eccentricity ecc $>$ 0.7.Besides we selected stars with effective temperature Teff > 4000 K, and APOGEE spectra with signal-to-noise S/N $>$ 100. This resulted in 52 stars, for which we intend to analyse spectra anddeduce their chemical abundances, in particular revising the APOGEE abundance results, and finally to understand their characteristics.