Year: 2024
Type: article
Abstract: The increasingly neutral intergalactic gas at z > 6 impacts the Lyman-α (Lyα) flux observed from galaxies. One luminous galaxy, COLA1, stands out because of its unique double-peaked Lyα line at z = 6.6, unseen in any simulation of reionization. Here, we present JWST/NIRCam wide-field slitless spectroscopy in a 21 arcmin2 field centered on COLA1. We find 141 galaxies spectroscopically selected through the [O III] doublet at 5.35 < z < 6.95, with 40 of these sources showing Hβ. For COLA1, we additionally detect [O III]4363 as well as Hγ. We measure a systemic redshift of z = 6.5917 for COLA1, confirming the classical double-peak nature of the Lyα profile. This implies that it resides in a highly ionized bubble and that it is leaking ionizing photons with a high escape fraction of fesc(LyC) = 20–50%, making it a prime laboratory to study Lyman continuum escape in the Epoch of Reionization. COLA1 shows all the signs of a prolific ionizer with a Lyα escape fraction of 81 ± 5%, Balmer decrement indicating no dust, a steep UV slope (βUV = −3.2 ± 0.4), and a star-formation surface density ≳10× that of typical galaxies at similar redshift. We detect five galaxies in COLA1’s close environment (Δz < 0.02). Exploiting the high spectroscopic completeness inherent to grism surveys, and using mock simulations that fully mimic the selection function, we show that the number of detected companions is very typical for a normal similarly UV-bright (MUV ∼ −21.3) galaxy – that is, the ionized bubble around COLA1 is unlikely to be due to an excessively large over-density. Instead, the measured ionizing properties suggest that COLA1 by itself might be powering the bubble required to explain its double-peaked Lyα profile (Rion ≈ 0.7 pMpc), with only minor contributions from detected neighbors (−19.5 ≲ MUV ≲ −17.5).
Institutions: Universitat de València, Parc Científic de la Universitat de València, Institute of Science and Technology Austria, Massachusetts Institute of Technology, ETH Zurich, University of Groningen, University of Copenhagen, University of Cambridge, National Astronomical Observatory of Japan, Center for Astrophysics Harvard & Smithsonian
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, National Aeronautics and Space Administration, Villum Fonden, Space Telescope Science Institute, European Commission, National Research Foundation, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Danmarks Grundforskningsfond, Generalitat Valenciana, Ministerio de Ciencia e Innovación, Staatssekretariat für Bildung, Forschung und Innovation, Agencia Estatal de Investigación
Awards: G103270039, G1338664626, G1422035950, G1855990336, G1890539920, Spectrometic and thermodynamic investigation of ion-solvent and ion-ligand interactions: Solvation in gaseous and liquid phases, G2262748287, G256731684, G2660406951, G3480869486, G3681454997, G3690828678, G3816317015, G4042783231, G425668148, Phasenübergänge und Instabilitäten, Cosmic Dawn Center (DAWN), G433322167, G4375798180, G4648019588, G4863782507, G5421974903, G5568641063, G5709720369, G58316358, G6273510985, G6920222135, G7084143925, G7751403103, G8684520763
OpenAlex ID: W6959842281
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