The imprint of clump formation at high redshift. II. The chemistry of the bulge

Abstract

In Paper I we showed that clumps in high-redshift galaxies, having a high star formation rate density (�SFR), produce disks with two tracks in the [Fe=H]-[�=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-�SFR clumpy 26 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 [�=Fe]. Thus clumpy star formation is able to simultaneously explain the chemodynamic trends of the MW's bulge, thin+thick disks and the Splash.