Spatially Resolved Physical Properties of Young Star Clusters and Star-forming Clumps in the Brightest z > 6 Galaxy, the Strongly Lensed Cosmic Spear at z = 6.2

@article{abdurrouf2026spatially,
  title = {{Spatially Resolved Physical Properties of Young Star Clusters and Star-forming Clumps in the Brightest z > 6 Galaxy, the Strongly Lensed Cosmic Spear at z = 6.2}},
  author = {Abdurro’uf and Dan Coe and Tom Resseguier and Calla Murphy and Xinfeng Xu and Angela Adamo and Namrata Roy and Alaina Henry and Vasily Kokorev and Gabriel Brammer and Seiji Fujimoto and Henry C. Ferguson and Amanda Pagul and Rogier A. Windhorst and Timothy Heckman and Jose M. Diego and Hollis B. Akins and Joseph F. V. Allingham and Ricardo O. Amorín and Danielle A. Berg and Maruša Bradač and Larry D. Bradley and Wenlei Chen and John Chisholm and Christopher J. Conselice and Pratika Dayal and Miroslava Dessauges-Zavadsky and Andreas L. Faisst and Steven L. Finkelstein and Yoshinobu Fudamoto and Lukas J. Furtak and Yuichi Harikane and Tiger Yu-Yang Hsiao and Yolanda Jimenez-Teja and Anton M. Koekemoer and Rebecca L. Larson and Ray A. Lucas and Matteo Messa and Lamiya Mowla and Minami Nakane and Gaël Noirot and Richard Pan and Massimo Pascale and Johan Richard and Massimo Ricotti and Luke Robbins and Daniel Schaerer and Fengwu Sun and Eros Vanzella and Brian Welch and Chris Willott and Adi Zitrin},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = nov,
  doi = {10.3847/1538-4357/aeab99},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/aeab99},
  note = {CC BY 4.0},
}

TY  - JOUR
TI  - Spatially Resolved Physical Properties of Young Star Clusters and Star-forming Clumps in the Brightest z > 6 Galaxy, the Strongly Lensed Cosmic Spear at z = 6.2
AU  - Abdurro’uf
AU  - Dan Coe
AU  - Tom Resseguier
AU  - Calla Murphy
AU  - Xinfeng Xu
AU  - Angela Adamo
AU  - Namrata Roy
AU  - Alaina Henry
AU  - Vasily Kokorev
AU  - Gabriel Brammer
AU  - Seiji Fujimoto
AU  - Henry C. Ferguson
AU  - Amanda Pagul
AU  - Rogier A. Windhorst
AU  - Timothy Heckman
AU  - Jose M. Diego
AU  - Hollis B. Akins
AU  - Joseph F. V. Allingham
AU  - Ricardo O. Amorín
AU  - Danielle A. Berg
AU  - Maruša Bradač
AU  - Larry D. Bradley
AU  - Wenlei Chen
AU  - John Chisholm
AU  - Christopher J. Conselice
AU  - Pratika Dayal
AU  - Miroslava Dessauges-Zavadsky
AU  - Andreas L. Faisst
AU  - Steven L. Finkelstein
AU  - Yoshinobu Fudamoto
AU  - Lukas J. Furtak
AU  - Yuichi Harikane
AU  - Tiger Yu-Yang Hsiao
AU  - Yolanda Jimenez-Teja
AU  - Anton M. Koekemoer
AU  - Rebecca L. Larson
AU  - Ray A. Lucas
AU  - Matteo Messa
AU  - Lamiya Mowla
AU  - Minami Nakane
AU  - Gaël Noirot
AU  - Richard Pan
AU  - Massimo Pascale
AU  - Johan Richard
AU  - Massimo Ricotti
AU  - Luke Robbins
AU  - Daniel Schaerer
AU  - Fengwu Sun
AU  - Eros Vanzella
AU  - Brian Welch
AU  - Chris Willott
AU  - Adi Zitrin
PY  - 2026
DA  - 2026/11/02
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/aeab99
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/aeab99
AB  - We present a spatially resolved analysis of stellar populations in the brightest z > 6 galaxy known to date (AB mag 23), the strongly lensed MACS0308−zD1 (dubbed the “Cosmic Spear”) at z spec = 6.2. New JWST NIRCam imaging and high-resolution NIRSpec integral field unit (IFU) spectroscopy span the rest-frame ultraviolet to optical. The NIRCam imaging reveals bright star-forming clumps and a tail consisting of three distinct, extremely compact star clusters that are multiply imaged by gravitational lensing. The star clusters have delensed effective radii of R eff ≲ 8 pc, stellar masses of M * ∼ 10 ⁶ –10 ⁷ M ⊙ , and high stellar mass surface densities of Σ * ≳ 2 × 10 ⁴ M ⊙ pc ⁻² . While their stellar populations are very young (∼6–11 Myr), their dynamical ages exceed unity, consistent with the clusters being gravitationally bound systems. Placing the star clusters in the size versus stellar mass density plane, we find they occupy a region similar to other high-redshift star clusters within galaxies observed recently with JWST, being significantly more massive and denser than local star clusters. Spatially resolved analysis of the brightest clump reveals a compact, intensely star-forming core. The ionizing photon production efficiency ( ξ ion ) is slightly suppressed in this central region, potentially indicating a locally elevated Lyman continuum escape fraction facilitated by feedback-driven channels.
SN  - 1538-4357
SN  - 0004-637X
ER  -