Timing the earliest quenching events with a robust sample of massive quiescent galaxies at 2 < z < 5. Issue 1 (4th June 2020)

• Record Type: Journal Article
• Authors: Carnall, A C; Walker, S; McLure, R J; Dunlop, J S; McLeod, D J; Cullen, F; Wild, V; Amorin, R; Bolzonella, M; Castellano, M; Cimatti, A; Cucciati, O; Fontana, A; Gargiulo, A; Garilli, B; Jarvis, M J; Pentericci, L; Pozzetti, L; Zamorani, G; Calabro, A; Hathi, N P; Koekemoer, A M
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 496:Issue 1(2020)
• Page Start: 695
• Page End: 707
• Publication Date: 2020-06-04
• Subjects: methods: statistical -- galaxies: evolution -- galaxies: star formation; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa1535
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We present a sample of 151 massive ( M * &gt; 10 10 M⊙ ) quiescent galaxies at 2 &lt; z &lt; 5, based on a sophisticated Bayesian spectral energy distribution fitting analysis of the CANDELS UDS and GOODS-South fields. Our sample includes a robust sub-sample of 61 objects for which we confidently exclude low-redshift and star-forming solutions. We identify 10 robust objects at z &gt; 3, of which 2 are at z &gt; 4. We report formation redshifts, demonstrating that the oldest objects formed at z &gt; 6; however, individual ages from our photometric data have significant uncertainties, typically ∼0.5 Gyr. We demonstrate that the UVJ colours of the quiescent population evolve with redshift at z &gt; 3, becoming bluer and more similar to post-starburst galaxies at lower redshift. Based upon this, we construct a model for the time evolution of quiescent galaxy UVJ colours, concluding that the oldest objects are consistent with forming the bulk of their stellar mass at z ∼ 6–7 and quenching at z ∼ 5. We report spectroscopic redshifts for two of our objects at z = 3.440 and 3.396, which exhibit extremely weak Ly α emission in ultra-deep VANDELS spectra. We calculate star formation rates based on these line fluxes, finding that these galaxies are consistent with our quiescent selection criteria, provided their Ly α escape fractions are &gt;3 and &gt;10 per cent, respectively. We finally report that our highest redshift robust object exhibits a continuum break at λ ∼ 7000 Å in a spectrum from VUDS, consistent with our photometric redshift of $z_\mathrm{phot}=4.72^{+0.06}_{-0.04}$ . If confirmed as quiescent, this object would be the highest redshift known quiescent galaxy. To obtain stronger constraints on the times of the earliest quenching events, high-SNR spectroscopy must be extended to z ≳ 3 quiescent objects.