Victoria Strait, Maruša Bradač, Dan Coe, Larry Bradley, Brett Salmon, Brian C. Lemaux, Kuang Han Huang, Adi Zitrin, Keren Sharon, Ana Acebron, Felipe Andrade-Santos, Roberto J. Avila, Brenda L. Frye, Austin Hoag, Guillaume Mahler, Mario Nonino, Sara Ogaz, Masamune Oguri, Masami Ouchi, Rachel Paterno-MahlerDebora Pelliccia

Research output: Contribution to journalArticlepeer-review


Measurements of stellar properties of galaxies when the universe was less than one billion years old yield some of the only observational constraints of the onset of star formation. We present here the inclusion of Spitzer/IRAC imaging in the spectral energy distribution fitting of the seven highest-redshift galaxy candidates selected from the Hubble Space Telescope imaging of the Reionization Lensing Cluster Survey (RELICS). We find that for 6/8 HST-selected z & 8 sources, the z & 8 solutions are still strongly preferred over z ∼1-2 solutions after the inclusion of Spitzer fluxes, and two prefer a z ∼ 7 solution, which we defer to a later analysis. We find a wide range of intrinsic stellar masses (5 × 106M – 4 × 109 M), star formation rates (0.2-14 Myr1), and ages (30-600 Myr) among our sample. Of particular interest is Abell1763-1434, which shows evidence of an evolved stellar population at z ∼ 8, implying its first generation of star formation occurred just < 100 Myr after the Big Bang. SPT0615-JD, a spatially resolved z ∼ 10 candidate, remains at its high redshift, supported by deep Spitzer/IRAC data, and also shows some evidence for an evolved stellar population. Even with the lensed, bright apparent magnitudes of these z & 8 candidates (H = 26.1-27.8 AB mag), only the James Webb Space Telescope will be able further confirm the presence of evolved stellar populations early in the universe.

Original languageEnglish (US)
JournalUnknown Journal
StatePublished - May 22 2019

ASJC Scopus subject areas

  • General

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