Massive Dead Galaxies at z ∼ 2 with HST Grism Spectroscopy. I. Star Formation Histories and Metallicity Enrichment

T. Morishita, L. E. Abramson, T. Treu, G. B. Brammer, T. Jones, P. Kelly, M. Stiavelli, M. Trenti, B. Vulcani, X. Wang

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Observations have revealed massive (log M∗/Mo ≳ 11) galaxies that were already dead when the universe was only ∼2 Gyr. Given the short time before these galaxies were quenched, their past histories and quenching mechanism(s) are of particular interest. In this paper, we study star formation histories (SFHs) of 24 massive galaxies at 1.6 < z < 2.5. A deep slitless spectroscopy and imaging data set collected from multiple Hubble Space Telescope surveys allows robust determination of their spectral energy distributions and SFHs with no functional assumption on their forms. We find that most of our massive galaxies had formed >50% of their extant masses by ∼1.5 Gyr before the time of observed redshifts, with a trend where more massive galaxies form earlier. Their stellar-phase metallicities are already compatible with those of local early-type galaxies, with a median value of log Z∗/Zo = 0.25 and scatter of ∼0.15 dex. In combination with the reconstructed SFHs, we reveal their rapid metallicity evolution from z ∼ 5.5 to ∼2.2 at a rate of ∼0.2 dex Gyr-1 in Z∗/Zo. Interestingly, the inferred stellar-phase metallicities are, when compared at half-mass time, ∼0.25 dex higher than observed gas-phase metallicities of star-forming galaxies. While systematic uncertainties remain, this may imply that these quenched galaxies have continued low-level star formation, rather than abruptly terminating their star formation activity, and kept enhancing their metallicity until recently.

Original languageEnglish (US)
Article number141
JournalAstrophysical Journal
Volume877
Issue number2
DOIs
StatePublished - Jun 1 2019

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metallicity
star formation
spectroscopy
histories
galaxies
history
gas
stopping
universe
quenching
vapor phases
trends
stars
rate
trend

Keywords

  • galaxies: abundances
  • galaxies: evolution
  • galaxies: formation
  • galaxies: high-redshift
  • galaxies: star formation

Cite this

Massive Dead Galaxies at z ∼ 2 with HST Grism Spectroscopy. I. Star Formation Histories and Metallicity Enrichment. / Morishita, T.; Abramson, L. E.; Treu, T.; Brammer, G. B.; Jones, T.; Kelly, P.; Stiavelli, M.; Trenti, M.; Vulcani, B.; Wang, X.

In: Astrophysical Journal, Vol. 877, No. 2, 141, 01.06.2019.

Research output: Contribution to journalArticle

Morishita, T, Abramson, LE, Treu, T, Brammer, GB, Jones, T, Kelly, P, Stiavelli, M, Trenti, M, Vulcani, B & Wang, X 2019, 'Massive Dead Galaxies at z ∼ 2 with HST Grism Spectroscopy. I. Star Formation Histories and Metallicity Enrichment', Astrophysical Journal, vol. 877, no. 2, 141. https://doi.org/10.3847/1538-4357/ab1d53
Morishita, T. ; Abramson, L. E. ; Treu, T. ; Brammer, G. B. ; Jones, T. ; Kelly, P. ; Stiavelli, M. ; Trenti, M. ; Vulcani, B. ; Wang, X. / Massive Dead Galaxies at z ∼ 2 with HST Grism Spectroscopy. I. Star Formation Histories and Metallicity Enrichment. In: Astrophysical Journal. 2019 ; Vol. 877, No. 2.
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