At the end of cosmic noon: Short gas depletion times in unobscured quasars at $z \sim$ 1

Understand

Unobscured quasars (QSOs) are predicted to be the final stage in the evolutionary sequence from gas-rich mergers to gas-depleted, quenched galaxies.

• Studies of this population, however, find a high incidence of far-infrared-luminous sources -suggesting significant dust-obscured star formation-but direct observations of the cold molecular gas fuelling this star formation are still necessary.
• We present a NOEMA study of CO(2-1) emission, tracing the cold molecular gas, in ten lensed z=1-1.5 unobscured QSOs.
• We detected CO(2-1) in seven of our targets, four of which also show continuum emission (\lambda_rest = 1.3mm).