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arXiv · 2003.04342

The Typical Massive Quiescent Galaxy at z$\sim$3 is a Post-starburst

C. D'Eugenio·E. Daddi·R. Gobat·V. Strazzullo·P. Lustig·I. Delvecchio·S. Jin·A. Puglisi·A. Calabró·C. Mancini·M. Dickinson·A. Cimatti·M. Onodera
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Abstract

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.

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C. D'Eugenio, E. Daddi, R. Gobat, V. Strazzullo, P. Lustig, I. Delvecchio, S. Jin, A. Puglisi, A. Calabró, C. Mancini, M. Dickinson, A. Cimatti, M. Onodera. 2020-03-09. The Typical Massive Quiescent Galaxy at z$\sim$3 is a Post-starburst. https://doi.org/10.3847/2041-8213/ab7a96

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