The Similarity of Abundance Ratio Trends and Nucleosynthetic Patterns in the Milky Way Disk and Bulge

Griffith, Emily; Weinberg, David H.; Johnson, Jennifer A.; Beaton, Rachael; García-Hernández, D. A.; Hasselquist, Sten; Holtzman, Jon; Johnson, James W.; Jönsson, Henrik; Lane, Richard R.; Nataf, David M.; Roman-Lopes, Alexandre
Referencia bibliográfica

The Astrophysical Journal

Fecha de publicación:
3
2021
Número de autores
12
Número de autores del IAC
1
Número de citas
44
Número de citas referidas
38
Descripción
We compare abundance ratio trends in a sample of ∼11,000 Milky Way bulge stars (RGC < 3 kpc) from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) to those of APOGEE stars in the Galactic disk (5 kpc < RGC < 11 kpc). We divide each sample into low-Ia (high-[Mg/Fe]) and high-Ia (low-[Mg/Fe]) populations, and in each population, we examine the median trends of [X/Mg] versus [Mg/H] for elements X = Fe, O, Na, Al, Si, P, S, K, Ca, V, Cr, Mn, Co, Ni, Cu, and Ce. To remove small systematic trends of APOGEE abundances with stellar $\mathrm{log}(g)$ , we resample the disk stars to match the $\mathrm{log}(g)$ distributions of the bulge data. After doing so, we find nearly identical median trends for low-Ia disk and bulge stars for all elements. High-Ia trends are similar for most elements, with noticeable (0.05-0.1 dex) differences for Mn, Na, and Co. The close agreement of abundance trends (with typical differences ≲0.03 dex) implies that similar nucleosynthetic processes enriched bulge and disk stars despite the different star formation histories and physical conditions of these regions. For example, we infer that differences in the high-mass slope of the stellar initial mass function between disk and bulge must have been ≲0.30. This agreement, and the generally small scatter about the median sequences, means that one can predict all of a bulge star's APOGEE abundances with good accuracy knowing only its measured [Mg/Fe] and [Mg/H] and the observed trends of disk stars.
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