Star formation under a cosmic microscope: highly magnified z = 11 galaxy behind the bullet cluster

Bradač, Maruša (author), Judež, Jon (author), Rihtaršič, Gregor (author), Martis, Nicholas S. (author), Harshan, Anishya (author), Felicioni, Giordano (author), Markov, Vladan (author), Tripodi, Roberta (author)

We present measurements of stellar population properties of a newly discovered, spectroscopically confirmed, $z=11.10^{+0.11}_{-0.26}$, gravitationally lensed galaxy, using JWST NIRSpec PRISM spectroscopy and NIRCam imaging. The arc is highly magnified by the Bullet Cluster (magnification factor $\mu=14.0^{+6.2}_{-0.3}$). It contains three star-forming components of which one is barely resolved and two are unresolved, giving intrinsic sizes of $\lesssim 10$ pc. The clumps also contain $\sim 50\%$ of the total stellar mass. The galaxy formed the majority of its stars $\sim 150$ Myr ago (by $z \sim 14$). The spectrum shows a pronounced damping wing, typical for galaxies deep in the reionization era and indicating a neutral intergalactic medium at this line of sight. The intrinsic luminosity of the galaxy is $0.086^{+0.008}_{-0.030} L^*$ (with $L^*$ being the characteristic luminosity for this redshift), making it the lowest-luminosity spectroscopically confirmed galaxy at $z > 10$ discovered to date.

• Language: English
• Keywords: galaxies, gravitational lensing, spectroscopy, photometry
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 8 str.
• Numbering: Vol. 995, no. 2, art. no. L74
• PID: 20.500.12556/RUL-178340
• UDC: 524.8
• ISSN on article: 2041-8213
• DOI: 10.3847/2041-8213/ae27d2
• COBISS.SI-ID: 265898243
• Publication date in RUL: 23.01.2026

Record is a part of a journal

• Title: The Astrophysical journal. Letters
• Shortened title: Astrophys. J. Lett.
• Publisher: American Astronomical Society
• ISSN: 2041-8213
• COBISS.SI-ID: 367233

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: galaksije, gravitacijsko lečenje, spektroskopija, fotometrija