The Imprint of Clump Formation at High Redshift. II. The Chemistry of the Bulge


In Paper I, we showed that clumps in high-redshift galaxies, having a high star formation rate density (ΣSFR), produce disks with two tracks in the [Fe/H]–[α/Fe] chemical space, similar to that of the Milky Way's (MW's) thin+thick disks. Here we investigate the effect of clumps on the bulge's chemistry. The chemistry of the MW's bulge is comprised of a single track with two density peaks separated by a trough. We show that the bulge chemistry of an N-body + smoothed particle hydrodynamics clumpy simulation also has a single track. Star formation within the bulge is itself in the high-ΣSFR clumpy mode, which ensures that the bulge's chemical track follows that of the thick disk at low [Fe/H] and then extends to high [Fe/H], where it peaks. The peak at low metallicity instead is comprised of a mixture of in situ stars and stars accreted via clumps. As a result, the trough between the peaks occurs at the end of the thick disk track. We find that the high-metallicity peak dominates near the mid-plane and declines in relative importance with height, as in the MW. The bulge is already rapidly rotating by the end of the clump epoch, with higher rotation at low [α/Fe]. Thus clumpy star formation is able to simultaneously explain the chemodynamic trends of the MW's bulge, thin+thick disks, and the splash.



Galactic bulge (2041), Milky Way formation (1053), Milky Way evolution (1052), Milky Way dynamics (1051), Galaxy bulges (578)


Debattista, Victor P., David J. Liddicott, Oscar A. Gonzalez, Leandro Beraldo e Silva, João AS Amarante, Ilin Lazar, Manuela Zoccali et al. "The imprint of clump formation at high redshift. II. The chemistry of the bulge." The Astrophysical Journal 946, no. 2 (2023): 118.
Copyright (c) 2002-2022, LYRASIS. All rights reserved.