RELICS: Properties of z ≥ 5.5 Galaxies Inferred from Spitzer and Hubble Imaging, Including A Candidate z ∼ 6.8 Strong [O iii] emitter
Victoria Strait, Maruša Bradač, Dan Coe, Brian C. Lemaux, Adam C. Carnall, Larry Bradley, Debora Pelliccia, Keren Sharon, Adi Zitrin, Ana Acebron, Chloe Neufeld, Felipe Andrade-Santos, Roberto J. Avila, Brenda L. Frye, Guillaume Mahler, Mario Nonino, Sara Ogaz, Masamune Oguri, Masami Ouchi, Rachel Paterno-Mahler, Daniel P. Stark, Ramesh Mainali, Pascal A. Oesch, Michele Trenti, Daniela Carrasco, William A. Dawson, Christine Jones, Keiichi Umetsu, Benedetta Vulcani
Abstract
Abstract We present constraints on the physical properties (including stellar mass, age, and star formation rate) of 207 6 ≲ z ≲ 8 galaxy candidates from the Reionization Lensing Cluster Survey (RELICS) and Spitzer-RELICS surveys. We measure photometry using T-PHOT and perform spectral energy distribution fitting using EA z Y and BAGPIPES. Of the 207 candidates for which we could successfully measure (or place limits on) Spitzer fluxes, 23 were demoted to likely z < 4. Among the high- z candidates, we find intrinsic stellar masses between 1 × 10 6 M ⊙ and 4 × 10 9 M ⊙ , and rest-frame UV absolute magnitudes between −22.6 and −14.5 mag. While our sample is mostly comprised of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>L</mml:mi> <mml:mrow> <mml:mi>m</mml:mi> <mml:mi>UV</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="true">/</mml:mo> <mml:msubsup> <mml:mi>L</mml:mi> <mml:mrow> <mml:mi>m</mml:mi> <mml:mi>UV</mml:mi> </mml:mrow> <mml:mo>*</mml:mo> </mml:msubsup> <mml:mo><</mml:mo> <mml:mn>1</mml:mn> </mml:math> galaxies, it extends to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>L</mml:mi> <mml:mrow> <mml:mi>m</mml:mi> <mml:mi>UV</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="true">/</mml:mo> <mml:msubsup> <mml:mi>L</mml:mi> <mml:mrow> <mml:mi>m</mml:mi> <mml:mi>UV</mml:mi> </mml:mrow> <mml:mo>*</mml:mo> </mml:msubsup> <mml:mo>∼</mml:mo> <mml:mn>2</mml:mn> </mml:math> . Our sample spans ∼4 orders of magnitude in stellar mass and star formation rates, and exhibits ages that range from maximally young to maximally old. We highlight 11 z ≥ 6.5 galaxies with detections in Spitzer/IRAC imaging, several of which show evidence for some combination of evolved stellar populations, large contributions of nebular emission lines, and/or dust. Among these is PLCKG287+32-2013, one of the brightest z ∼ 7 candidates known (AB mag 24.9 at 1.6 μ m) with a Spitzer 3.6 μ m flux excess suggesting strong [O iii ] + H- β emission (∼1000 Å rest-frame equivalent width). We discuss the possible uses and limits of our sample and present a public catalog of Hubble + Spitzer photometry along with physical property estimates for all objects in the sample. Because of their apparent brightnesses, high redshifts, and variety of stellar populations, these objects are excellent targets for follow-up with the James Webb Space Telescope.