Fossil imprints of outflow from the galactic bulge in elemental abundances of metal-rich disk stars

We explore the elemental abundance features of metal-rich disk stars, highlighting a comparison with the recently revealed Galactic bulge stars. A similarity in two features leads to a new theoretical picture of the bulge-disk connection in the Galaxy, where a supermassive black hole resides at the center. We postulate that a metal-rich outflow, triggered by feedback from a black hole, quenched the star formation that had lasted several billion years in the bulge. The expelled gas cooled down in the Galactic halo without escaping from the gravitational potential of the Galaxy. The gas gradually started to accrete into the disk around five billion years ago, corresponding to the time of the Sun's birth, and replaced a low-metallicity halo gas that had been accreting over nearly ten billion years. The metal-rich infalling gas, whose elemental abundance reflects that of metal-rich bulge stars, mixed with the interstellar gas already present in the disk. Stars formed from the mixture now compose the metal-rich stellar disk. This scheme is incorporated into models for the chemical evolution of the disk. The resultant elemental features are compatible with the observed abundance trends of metal-rich disk stars, including the upturning feature exhibited in some [X/Fe] ratios, the interpretation of which was theoretically puzzling. Furthermore, the predicted abundance distribution function of disk stars covers all observational facts to be considered: (1) the deficiency of metal-poor stars, (2) the location of the [Fe/H] peak, and (3) the extended metal-rich tail up to. [Fe/H] similar to +0.4.