Vol. 542
In section 1. Letters

ALMA reveals a chemically evolved submillimeter galaxy at z=4.76

by T. Nagao, R. Maiolino, C. De Breuck, P. Caselli, B. Hatsukade, and K. Saigo, A&A 542, L34


ALMA early science is providing new discoveries: the redshifted far-infrared fine-structure emission lines [NII]205micron and [CII]158micron were detected in a z=4.76 submillimeter Galaxy (SMG). *The metallicity of this very obscured object was derived, but rest-frame optical emission lines are unusable for these dust-enshrouded galaxies. The velocity-integrated [NII]/[CII] flux ratio is 0.043, quite similar to the ratio observed in the nearby universe. Together with photoionization models this suggests that the metallicity in this SMG is consistent with solar, which means that the chemical evolution has been very rapid in this system at z=4.76.