Recent star formation in a massive slowly quenched lensed quiescent galaxy at z=1.88

Mohammad Akhshik, Katherine E. Whitaker, Joel Leja, Guillaume Mahler, Keren Sharon, Gabriel Brammer, Sune Toft, Rachel Bezanson, Allison Man, Erica J. Nelson, Camilla Pacifici, Sarah Wellons, Christina C. Williams

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


In this Letter, we reconstruct the formation pathway of MRG-S0851, a massive, logM*M⊙ = 11.02 ±0.04, strongly lensed, red galaxy at z = 1.883 ± 0.001. While the global photometry and spatially resolved outskirts of MRG-S0851 imply an early formation scenario with a slowly decreasing or constant star formation history, a joint fit of 2D grism spectroscopy and photometry reveals a more complex scenario: MRG-S0851 is likely to be experiencing a centrally concentrated rejuvenation in the inner ∼1 kpc in the last ∼100 Myr of evolution. We estimate 0.5 ± 0.1% of the total stellar mass is formed in this phase. Rejuvenation episodes are suggested to be infrequent for massive galaxies at z ∼ 2, but as our analyses indicate, more examples of complex star formation histories may yet be hidden within existing data. By adding an FUV color criterion to the standard U-V/V-J diagnostic-thereby heightening our sensitivity to recent star formation-we show that we can select populations of galaxies with similar spectral energy distributions to that of MRG-S0851, but note that deep follow-up spectroscopic observations and/or spatially resolved analyses are necessary to robustly confirm the rejuvenation of these candidates. Using our criteria with MRG-S0851 as a prototype, we estimate that ∼1% of massive quiescent galaxies at 1 < z < 2 are potentially rejuvenating.

Original languageEnglish (US)
Article numberabd416
JournalAstrophysical Journal Letters
Issue number1
StatePublished - Jan 20 2021

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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