The nature of an ultra-faint galaxy in the cosmic dark ages seen with JWST
Article 2023 en
Authors
GR
Guido Roberts-Borsani
TT
Tommaso Treu
WC
Wenlei Chen
Abstract
1 min read
In the first billion years after the Big Bang, sources of ultraviolet (UV) photons are believed to have ionized intergalactic hydrogen, rendering the Universe transparent to UV radiation. Galaxies brighter than the characteristic luminosity L* (refs. <sup>1,2</sup>) do not provide enough ionizing photons to drive this cosmic reionization. Fainter galaxies are thought to dominate the photon budget; however, they are surrounded by neutral gas that prevents the escape of the Lyman-α photons, which has been the dominant way to identify them so far. JD1 was previously identified as a triply-imaged galaxy with a magnification factor of 13 provided by the foreground cluster Abell 2744 (ref. <sup>3</sup>), and a photometric redshift of z ≈ 10. Here we report the spectroscopic confirmation of this very low luminosity (≈0.05 L*) galaxy at z = 9.79, observed 480 Myr after the Big Bang, by means of the identification of the Lyman break and redward continuum, as well as multiple ≳4σ emission lines, with the Near-InfraRed Spectrograph (NIRSpec) and Near-InfraRed Camera (NIRCam) instruments. The combination of the James Webb Space Telescope (JWST) and gravitational lensing shows that this ultra-faint galaxy (M<sub>UV</sub> = -17.35)-with a luminosity typical of the sources responsible for cosmic reionization-has a compact (≈150 pc) and complex morphology, low stellar mass (10<sup>7.19</sup> M<sub>⊙</sub>) and subsolar (≈0.6 Z<sub>⊙</sub>) gas-phase metallicity.
Guido Roberts-Borsani, Tommaso Treu, Wenlei Chen, Takahiro Morishita, E. Vanzella, Adi Zitrin, P. Bergamini, M. Castellano, A. Fontana, C. Grillo, Patrick L. Kelly, E. Merlin, D. Paris, P. Rosati, Ana Acebrón, Andrea Bonchi, Kristan Boyett, Maruša Bradač, Tom Broadhurst, Antonello Calabrò, J. M. Diego, Alan Dressler, Lukas J. Furtak, Alexei V Filippenko, Karl Glazebrook, Anton M. Koekemoer, Nicha Leethochawalit, Matthew A. Malkan, Charlotte Mason, A. Mercurio, Benjamin Metha, Themiya Nanayakkara, L. Pentericci, Justin Pierel, Steven Rieck, Namrata Roy, P. Santini, Victoria Strait, R. Strausbaugh, Michele Trenti, Benedetta Vulcani, Lifan Wang, Xin Wang, Rogier A. Windhorst, Lilan Yang
Hayley Williams, Patrick L. Kelly, Wenlei Chen, Gabriel Brammer, Adi Zitrin, Tommaso Treu, Claudia Scarlata, Anton M. Koekemoer, Masamune Oguri, Yuheng Lin, J. M. Diego, M. Nonino, J. Hjorth, Tom Broadhurst, Noah S. J. Rogers, I. Pérez‐Fournon, R. J. Foley, Saurabh W. Jha, Alexei V Filippenko, Lou Strolger, Justin Pierel, F. Poidevin
Hayley Williams, Patrick L. Kelly, Wenlei Chen, Gabriel Brammer, Adi Zitrin, Tommaso Treu, Claudia Scarlata, Anton M. Koekemoer, Masamune Oguri, Yu-Heng Lin, J. M. Diego, M. Nonino, J. Hjorth, Danial Langeroodi, Tom Broadhurst, Noah S. J. Rogers, I. Pérez‐Fournon, R. J. Foley, Saurabh W. Jha, Alexei V Filippenko, Lou Strolger, Justin Pierel, F. Poidevin, Lilan Yang
M. Castellano, Lorenzo Napolitano, A. Fontana, Guido Roberts-Borsani, Tommaso Treu, E. Vanzella, Jorge A. Zavala, Pablo Arrabal Haro, Antonello Calabrò, Mario Llerena, Sara Mascia, E. Merlin, D. Paris, L. Pentericci, P. Santini, Tom J. L. C. Bakx, P. Bergamini, G. Cupani, Mark Dickinson, Alexei V Filippenko, Karl Glazebrook, C. Grillo, Patrick L. Kelly, Matthew A. Malkan,
M. Castellano, Lorenzo Napolitano, A. Fontana, Guido Roberts-Borsani, Tommaso Treu, E. Vanzella, Jorge A. Zavala, Pablo Arrabal Haro, Antonello Calabrò, Mario Llerena, Sara Mascia, E. Merlin, D. Paris, L. Pentericci, P. Santini, Tom J. L. C. Bakx, P. Bergamini, G. Cupani, Mark Dickinson, Alexei V Filippenko, Karl Glazebrook, C. Grillo, Patrick L. Kelly, Matthew A. Malkan,
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