http://arxiv.org/abs/2003.04342
We have obtained spectroscopic confirmation with Hubble Space Telescope WFC3/G141 of a first sizeable sample of nine quiescent galaxies at 2.4<z<3.3. Their average near-UV/optical rest-frame spectrum is characterized by low attenuation (Av$\sim$0.6 mag) and a strong Balmer break, larger than the 4000 A break, corresponding to a fairly young age of $\sim$300 Myr. This formally classifies a substantial fraction of classically selected quiescent galaxies at z $\sim$ 3 as post-starbursts, marking their convergence to the quenching epoch. The rapid spectral evolution with respect to z $\sim$ 1.5 quiescent galaxies is not matched by an increase of residual star-formation, as judged from the weak detection of [O II]3727A emission, pointing to a flattening of the steep increase in gas fractions previously seen from z $\sim$ 0 to 1.8. However, radio 3GHz stacked emission implies either much stronger dust-obscured star formation or substantial further evolution in radio-mode AGN activity with respect to z $\sim$ 1.5.
C. D’Eugenio, E. Daddi, R. Gobat, et. al.
Wed, 11 Mar 20
26/65
Comments: 8 pages, 4 figures. To appear on ApJ Letters
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