The Early Early Type: Discovery of a Passive Galaxy at $_{Zspec}$ $\sim$ 3
Résumé
We present the discovery of a massive, quiescent galaxy at $z$ = 2.99. We have obtained an $Hubble\ Space\ Telescope$ WFC3 spectrum of this object and measured its redshift from the detection of a deep 4000 $\mathring{A}$ break consistent with an old population and a high metallicity. By stellar population modeling of both its grism spectrum and broadband photometry, we derive an age of $\sim$0.7 Gyr, implying a formation redshift of $z$ > 4, and a mass >10$^{11}$ $M \odot$. Although this passive galaxy is the most distant confirmed so far, we find that it is slightly less compact than other $z$ > 2 early types of similar mass, being overall more analogous to those $z$ $\sim$ 1.6 field early-type galaxies. The discovery of this object shows that early-type galaxies are detectable to at least $z$ = 3 and suggests that the diversity of structural properties found in $z$ = 1.4-2 ellipticals to earlier epochs could have its origin in a variety of formation histories among their progenitors.
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