High-redshift Galaxy Candidates at z = 9–10 as Revealed by JWST Observations of WHL0137-08
Larry Bradley, Dan Coe, Gabriel Brammer, Lukas J. Furtak, Rebecca L. Larson, Vasily Kokorev, Felipe Andrade-Santos, Rachana Bhatawdekar, Maruša Bradač, Tom Broadhurst, Adam C. Carnall, Christopher J. Conselice, J. M. Diego, Brenda Frye, Seiji Fujimoto, Tiger Yu-Yang Hsiao, Taylor A. Hutchison, Intae Jung, Guillaume Mahler, Stephan R. McCandliss, Masamune Oguri, Marc Postman, Keren Sharon, Michele Trenti, E. Vanzella, Brian Welch, Rogier A. Windhorst, Adi Zitrin
Abstract
Abstract We report the discovery of four galaxy candidates observed 450–600 Myr after the Big Bang with photometric redshifts between z ∼ 8.3 and 10.2 measured using James Webb Space Telescope (JWST) NIRCam imaging of the galaxy cluster WHL0137−08 observed in eight filters spanning 0.8–5.0 μ m, plus nine Hubble Space Telescope filters spanning 0.4–1.7 μ m. One candidate is gravitationally lensed with a magnification of μ ∼ 8, while the other three are located in a nearby NIRCam module with expected magnifications of μ ≲ 1.1. Using SED fitting, we estimate the stellar masses of these galaxies are typically in the range <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> = 8.3–8.7. All appear young, with mass-weighted ages <240 Myr, low dust content A V < 0.15 mag, and specific star formation rates sSFR ∼0.25–10 Gyr −1 for most. One z ∼ 9 candidate is consistent with an age <5 Myr and an sSFR ∼10 Gyr −1 , as inferred from a strong F444W excess, implying [O iii ]+H β rest-frame equivalent width ∼2000 Å, although an older z ∼ 10 object is also allowed. Another z ∼ 9 candidate is lensed into an arc 2.″4 long with a magnification of μ ∼ 8. This arc is the most spatially resolved galaxy at z ∼ 9 known to date, revealing structures ∼30 pc across. Follow-up spectroscopy of WHL0137−08 with JWST/NIRSpec will be useful to spectroscopically confirm these high-redshift galaxy candidates and to study their physical properties in more detail.