The <i>z</i> = 9.625 Cosmic Gems galaxy was a compact “blue monster” propelled by massive star clusters
The recent discovery of five massive stellar clusters at z = 9.625 in the Cosmic Gems galaxy has raised the question about the formation mechanism of star clusters in the first 500 Myr after the Big Bang. We inferred the total stellar mass in clusters by normalizing and integrating the stellar cluster mass function (SCMF, d n ( M )/d M = n 0 M β ), assuming three different slopes ( β = −1.5, −2.0, and −2.5) and different lower-mass limits between 10 2 and 10 5 M ⊙ . We compared the total integrated cluster stellar mass to the stellar mass inferred from the counter image of the Cosmic Gems, which provides the best modestly magnified ( μ = 1.84 ± 0.05) representation of the entire galaxy. The delensed stellar mass of the Cosmic Gems galaxy was estimated as 3.5 −1.8 +3.3 × 10 7 M ⊙ , with an effective radius of R eff = 103 −15 +13 parsecs and a stellar surface mass density of Σ mass = 520 −225 +340 M ⊙ pc −2 . Accounting for normalization uncertainties – including different lensing magnification scenarios for the arc – a modified SCMF, combined with a significantly high star cluster formation efficiency (approaching 100%), appears to be a necessary condition to explain the relatively short formation timescale of both the star clusters and the counter image, without exceeding the galaxy’s stellar mass. By extrapolating the physical properties at the peak of the burst, we found that in its recent past (≲30 Myr) the Cosmic Gems galaxy likely experienced a specific star formation rate exceeding 25 Gyr −1 and luminosity approaching the “blue monster” regime ( M UV < −20). Our study provides insights into the extreme clustered nature of star formation in early galaxies and sheds light on the formation of bound star clusters that might survive to z = 0 as globular clusters older than 13 Gyr.
Authors
- A. Zanella
- C. Grillo
- Colin Norman (ORCID: https://orcid.org/0000-0002-5222-5717)
- Maruša Bradač (ORCID: https://orcid.org/0000-0001-5984-0395)
- Adélaïde Claeyssens (ORCID: https://orcid.org/0000-0001-7940-1816)
- P. Rosati
- Massimo Ricotti (ORCID: https://orcid.org/0000-0003-4223-7324)
- E. Zackrisson
- A. Bolamperti (ORCID: https://orcid.org/0000-0001-5976-9728)
- Keren Sharon (ORCID: https://orcid.org/0000-0002-7559-0864)
- F. Loiacono (ORCID: https://orcid.org/0000-0002-8858-6784)
- L. Christensen (ORCID: https://orcid.org/0000-0001-8415-7547)
- Abdurrouf (ORCID: https://orcid.org/0000-0002-5258-8761)
- F. E. Bauer (ORCID: https://orcid.org/0000-0002-8686-8737)
- Johan Richard (ORCID: https://orcid.org/0000-0001-5492-1049)
- Matteo Messa (ORCID: https://orcid.org/0000-0003-1427-2456)
- S. Fujimoto
- Angela Adamo (ORCID: https://orcid.org/0000-0002-8192-8091)
- E. Vanzella
- Rachana Bhatawdekar (ORCID: https://orcid.org/0000-0003-0883-2226)
- Larry Bradley (ORCID: https://orcid.org/0000-0002-7908-9284)
- Takuya Hashimoto (ORCID: https://orcid.org/0000-0002-0898-4038)
- Yolanda Jiménez-Teja (ORCID: https://orcid.org/0000-0002-6090-2853)
- Dan Coe (ORCID: https://orcid.org/0000-0001-7410-7669)
- Arjan Bik (ORCID: https://orcid.org/0000-0001-8068-0891)
- M. Trenti
- Tiger Yu-Yang Hsiao (ORCID: https://orcid.org/0000-0003-4512-8705)
- F. Calura (ORCID: https://orcid.org/0000-0002-6175-0871)
- Brenda Frye (ORCID: https://orcid.org/0000-0003-1625-8009)
- Xinfeng Xu (ORCID: https://orcid.org/0000-0002-9217-7051)
- M. Lombardi (ORCID: https://orcid.org/0000-0002-3336-4965)
- P. Bergamini (ORCID: https://orcid.org/0000-0003-1383-9414)
- Jane R. Rigby (ORCID: https://orcid.org/0000-0002-7627-6551)
- Akio Inoue (ORCID: https://orcid.org/0000-0002-7779-8677)
- Masamune Oguri (ORCID: https://orcid.org/0000-0003-3484-399X)
- Brian T. Welch (ORCID: https://orcid.org/0000-0003-2092-3163)
- Adi Zitrin (ORCID: https://orcid.org/0000-0002-0350-4488)
- J. M. Diego (ORCID: https://orcid.org/0000-0001-9065-3926)
- P. Bergamini
- Tom Resseguier (ORCID: https://orcid.org/0009-0007-0522-7326)
Institutions
- Université Claude Bernard Lyon 1 (FR)
- École Normale Supérieure de Lyon (FR)
- Uppsala University (SE)
- University of Copenhagen (DK)
- Ben-Gurion University of the Negev (IL)
- Centre National de la Recherche Scientifique (FR)
- Space Telescope Science Institute (US)
- Goddard Space Flight Center (US)
- Johns Hopkins University (US)
- University of Tsukuba (JP)
- Waseda University (JP)
- University of Ljubljana (SI)
- Chiba University (JP)
- The University of Melbourne (AU)
- Lyon College (US)
- University of Toronto (CA)
- University of Tarapacá (CL)
- University of Milan (IT)
- University of Ferrara (IT)
- University of Michigan (US)
- European Space Agency (FR)
- Dawn Research (United States) (US)
- Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna (IT)
- Valongo Observatory (BR)
- European Space Astronomy Centre (ES)
- Max Planck Institute for Astrophysics (DE)
- DAWN Center for Independent Living (US)
- Schnörringen Telescope Science Institute (DE)
- Center for Astrophysics Harvard & Smithsonian (US)
- AlbaNova (SE)
- Instituto de Física de Cantabria (ES)
- Astronomical Observatory (RS)
- ARC Centre of Excellence for All-sky Astrophysics (AU)
- Instituto de Astrofísica de Andalucía (ES)
- University of Maryland, College Park (US)
- National Institute for Astrophysics (IT)
Publication Details
- Journal
- Astronomy and Astrophysics
- Published
- 2025-12-01
- DOI
- https://doi.org/10.1051/0004-6361/202556570
- Citations
- 1
- Primary Topic
- Galaxies: Formation, Evolution, Phenomena
- Type
- article
- Field-Weighted Citation Impact
- 1.15