_version_ 1866909950505123840
author Abdurro'uf
Coe, Dan
Resseguier, Tom
Murphy, Calla
Xu, Xinfeng
Adamo, Angela
Roy, Namrata
Henry, Alaina
Kokorev, Vasily
Brammer, Gabriel
Fujimoto, Seiji
Ferguson, Henry C.
Pagul, Amanda
Windhorst, Rogier A.
Heckman, Timothy
Diego, Jose M.
Akins, Hollis B.
Allingham, Joseph
Amorín, Ricardo O.
Berg, Danielle A.
Bradač, Maruša
Bradley, Larry D.
Chen, Wenlei
Chisholm, John
Conselice, Christopher J.
Dayal, Pratika
Dessauges-Zavadsky, Miroslava
Faisst, Andreas L.
Finkelstein, Steven L.
Fudamoto, Yoshinobu
Furtak, Lukas J.
Harikane, Yuichi
Hsiao, Tiger Yu-Yang
Jimenez-Teja, Yolanda
Koekemoer, Anton M.
Larson, Rebecca L.
Lucas, Ray A.
Messa, Matteo
Mowla, Lamiya
Nakane, Minami
Noirot, Gaël
Pan, Richard
Pascale, Massimo
Richard, Johan
Ricotti, Massimo
Robbins, Luke
Schaerer, Daniel
Sun, Fengwu
Vanzella, Eros
Welch, Brian
Willott, Chris
Zitrin, Adi
author_facet Abdurro'uf
Coe, Dan
Resseguier, Tom
Murphy, Calla
Xu, Xinfeng
Adamo, Angela
Roy, Namrata
Henry, Alaina
Kokorev, Vasily
Brammer, Gabriel
Fujimoto, Seiji
Ferguson, Henry C.
Pagul, Amanda
Windhorst, Rogier A.
Heckman, Timothy
Diego, Jose M.
Akins, Hollis B.
Allingham, Joseph
Amorín, Ricardo O.
Berg, Danielle A.
Bradač, Maruša
Bradley, Larry D.
Chen, Wenlei
Chisholm, John
Conselice, Christopher J.
Dayal, Pratika
Dessauges-Zavadsky, Miroslava
Faisst, Andreas L.
Finkelstein, Steven L.
Fudamoto, Yoshinobu
Furtak, Lukas J.
Harikane, Yuichi
Hsiao, Tiger Yu-Yang
Jimenez-Teja, Yolanda
Koekemoer, Anton M.
Larson, Rebecca L.
Lucas, Ray A.
Messa, Matteo
Mowla, Lamiya
Nakane, Minami
Noirot, Gaël
Pan, Richard
Pascale, Massimo
Richard, Johan
Ricotti, Massimo
Robbins, Luke
Schaerer, Daniel
Sun, Fengwu
Vanzella, Eros
Welch, Brian
Willott, Chris
Zitrin, Adi
contents We present 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 $z_{\rm spec}=6.2$. New JWST NIRCam imaging and high-resolution NIRSpec 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 effective radii of $R_{\rm{eff}} \sim 5$ pc, stellar masses of $M_{*} \sim 10^{6}-10^{7}\,M_{\odot}$, and high stellar mass surface densities of $Σ_{*} > 10^{4}\,M_{\odot}~\rm{pc}^{-2}$. While their stellar populations are very young ($\sim 5-9$ Myr), their dynamical ages exceed unity, consistent with the clusters being gravitationally bound systems. Placing the star clusters in the size vs.~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 ($ξ_{\rm{ion}}$) is slightly suppressed in this central region, potentially indicating a locally elevated Lyman continuum escape fraction facilitated by feedback-driven channels.
format Preprint
id arxiv_https___arxiv_org_abs_2512_08054
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle 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
Abdurro'uf
Coe, Dan
Resseguier, Tom
Murphy, Calla
Xu, Xinfeng
Adamo, Angela
Roy, Namrata
Henry, Alaina
Kokorev, Vasily
Brammer, Gabriel
Fujimoto, Seiji
Ferguson, Henry C.
Pagul, Amanda
Windhorst, Rogier A.
Heckman, Timothy
Diego, Jose M.
Akins, Hollis B.
Allingham, Joseph
Amorín, Ricardo O.
Berg, Danielle A.
Bradač, Maruša
Bradley, Larry D.
Chen, Wenlei
Chisholm, John
Conselice, Christopher J.
Dayal, Pratika
Dessauges-Zavadsky, Miroslava
Faisst, Andreas L.
Finkelstein, Steven L.
Fudamoto, Yoshinobu
Furtak, Lukas J.
Harikane, Yuichi
Hsiao, Tiger Yu-Yang
Jimenez-Teja, Yolanda
Koekemoer, Anton M.
Larson, Rebecca L.
Lucas, Ray A.
Messa, Matteo
Mowla, Lamiya
Nakane, Minami
Noirot, Gaël
Pan, Richard
Pascale, Massimo
Richard, Johan
Ricotti, Massimo
Robbins, Luke
Schaerer, Daniel
Sun, Fengwu
Vanzella, Eros
Welch, Brian
Willott, Chris
Zitrin, Adi
Astrophysics of Galaxies
We present 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 $z_{\rm spec}=6.2$. New JWST NIRCam imaging and high-resolution NIRSpec 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 effective radii of $R_{\rm{eff}} \sim 5$ pc, stellar masses of $M_{*} \sim 10^{6}-10^{7}\,M_{\odot}$, and high stellar mass surface densities of $Σ_{*} > 10^{4}\,M_{\odot}~\rm{pc}^{-2}$. While their stellar populations are very young ($\sim 5-9$ Myr), their dynamical ages exceed unity, consistent with the clusters being gravitationally bound systems. Placing the star clusters in the size vs.~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 ($ξ_{\rm{ion}}$) is slightly suppressed in this central region, potentially indicating a locally elevated Lyman continuum escape fraction facilitated by feedback-driven channels.
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
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2512.08054