A New Contributor to Chemical Evolution in High-Redshift Galaxies
  The recent discovery of a new population of stars exhibiting unusual elemental abundance patterns characterized by enhanced Ti to Ga elements and low alpha and n-capture elements suggests the contribution of a new class of supernovae, probably a kind of Type Ia supernovae associated with close binary evolution. The role of these supernovae in chemical evolution is negligible in normal galaxies that undergo moderate star formation such as our own. Thus, while the frequency of occurrence would be too low to detect in low-redshift galaxies, it may represent a prominent population in high-redshift objects such as early epoch massive elliptical galaxies and QSOs. The chemical contributor of this proposed type of supernovae in combination with recognized supernovae is shown to be compatible with the recent observational features in the distant universe, successfully reproducing the Type II supernovae-like abundance pattern with enhancement of Ga and Ge in the gas of newborn massive galaxies and high iron abundances in QSOs even at redshifts of around 6. 
Takuji Tsujimoto (National Astronomical Observatory of Japan)