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 (Σ SFR ), 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-Σ SFR 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.