Year: 2025
Type: article
Abstract: We report the discovery of an ultra-massive grand-design red spiral galaxy, named Zhúlóng (Torch Dragon), at $ z_{\mathrm{phot}} = 5.2^{+0.3}_{-0.2} $ in the JWST PANORAMIC survey; it is the most distant bulge+disk galaxy candidate with spiral arms known to date. Zhúlóng displays an extraordinary combination of properties: (1) a classical bulge centered in a large, face-on exponential stellar disk (half-light radius of Re = 3.7 ± 0.1 kpc) with spiral arms extending across 19 kpc; (2) a clear transition from the red, quiescent core (F150W − F444W = 3.1 mag) with a high stellar mass surface density ($ \log(\Sigma M_{\star}/M_{\odot}\,\mathrm{kpc}^{-2}) = 9.91_{-0.09}^{+0.11} $) to the star-forming outer regions, as revealed by spatially resolved spectral energy distribution analysis, which indicates significant inside-out galaxy growth; (3) an extremely high stellar mass for its redshift, with $ \log (M_{\star}/M_{\odot})=11.03_{-0.08}^{+0.10} $, which is comparable to the Milky Way’s mass, and an implied baryon-to-star conversion efficiency (ϵ ∼ 0.3) that is 1.5 times higher than even the most efficient galaxies at later epochs; and (4) despite an active disk, a relatively modest overall star formation rate ($ \mathrm{SFR} = 66_{-46}^{+89}\,M_{\odot} $ yr−1), which is > 0.5 dex below the star formation main sequence at z ∼ 5.2 and > 10 times lower than ultra-massive dusty galaxies at z = 5 − 6. Zhúlóng shows that mature galaxies emerged much earlier than previously believed, in the first billion years after the Big Bang, through rapid galaxy formation and morphological evolution. Our finding offers key constraints for models of massive galaxy formation and the origin of spiral structures in the early Universe.
Authors: Mengyuan Xiao, Christina C. Williams, Pascal A. Oesch, David Elbaz, Miroslava Dessauges-Zavadsky, Rui Marques-Chaves, Longji Bing, Zhiyuan Ji, Andrea Weibel, Rachel Bezanson, Gabriel Brammer, Caitlin Casey, Aidan P. Cloonan, Emanuele Daddi, Pratika Dayal, Andreas L. Faisst, Marijn Franx, Karl Glazebrook, Anne Hutter, Jeyhan S. Kartaltepe, Ivo Labbe, Guilaine Lagache, Seunghwan Lim, Benjamin Magnelli, Felix Martinez, Michael V. Maseda, Themiya Nanayakkara, Daniel Schaerer, Katherine E. Whitaker
Institutions: University of Geneva, University of Arizona, NSF NOIRLab, University of Copenhagen, Centre National de la Recherche Scientifique, Université Paris Cité, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Université Paris-Saclay, Astrophysique, Instrumentation et Modélisation, University of Sussex, University of Pittsburgh, University of Massachusetts Amherst, University of Groningen, California Institute of Technology, Infrared Processing and Analysis Center, Leiden University, Leiden Observatory, Swinburne University of Technology, Rochester Institute of Technology, Aix-Marseille Université, University of Cambridge, University of Wisconsin–Madison
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, University of Arizona, Space Telescope Science Institute, UK Research and Innovation, National Radio Astronomy Observatory, European Commission, National Research Foundation, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Rijksuniversiteit Groningen, Danmarks Grundforskningsfond, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Korea Astronomy and Space Science Institute, National Astronomical Observatory of Japan, National Science and Technology Council, Science and Technology Facilities Council, National Institutes of Natural Sciences, Staatssekretariat für Bildung, Forschung und Innovation
Awards: G103270039, University of Sussex Astronomy Consolidated Grant 2020-2023, G1166668239, G1338664626, Spectrometic and thermodynamic investigation of ion-solvent and ion-ligand interactions: Solvation in gaseous and liquid phases, G256731684, Characterizing Low-Mass Galaxies with Spectroscopy Through Cosmic Time, G3152952368, University of Sussex Astronomy Consolidated Grant 2023-2026, G3340416472, G3816317015, Cosmic Dawn Center (DAWN), G4501905872, G4550844739, G4648019588, G5568641063, ODIN: a framework to shed light on Dark Matter and the era of cosmic dawn, G7691714859, G8138827550, G971458805
OpenAlex ID: W6921932922
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