A massive barred spiral galaxy at z = 5.102 discovered by JWST

Xiaohan Wang; Fengwu Sun; Yoshihisa Asada; Yunjing Wu; Xiaojing Lin; Shude Mao; Sijia Cai; Zheng Cai; Chian-Chou Chen; Wenlei Chen; Cheng Cheng; Christopher J. Conselice; Miroslava Dessauges-Zavadsky; Daneil Espada; Brenda L. Frye; Jean-Baptiste Jolly; Anton M. Koekemoer; Kotaro Kohno; Mingyu Li; Nicholas Martis; Hideki Umehata; Weichen Wang; Rogier A. Windhorst; Adi Zitrin

arXiv · 2606.25022

A massive barred spiral galaxy at z = 5.102 discovered by JWST

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Abstract

We report M1149-BSG-z5, a barred spiral galaxy at $z = 5.102$, identified in the parallel field of MACS J1149+2223 with JWST and HST. M1149-BSG-z5 is the highest redshift barred galaxy candidate to date. Both isophote ellipse fitting and structural modeling support a stellar bar of length $a_\mathrm{bar} \approx 4.5$ kpc, and extended spiral arms peaking at $r \approx 5.5$ kpc. M1149-BSG-z5 is a massive main sequence star-forming galaxy, with a stellar mass of $10^{10.45}\rm M_\odot$ and a star-formation rate of $144\,\rm M_\odot/yr$. A concentrated bulge is embedded in an extended disk with a global S\'ersic index $n = 2.37$. With an effective radius of $R_{e} = 2.61\rm \ kpc$, M1149-BSG-z5 is larger than typical galaxies at $z \sim 5$ and comparable to barred galaxies at $2 < z < 4$. M1149-BSG-z5 also hosts a broad-line AGN, with a relatively low black-hole-to-stellar mass ratio of $\rm M_{\rm BH}/M_\ast\sim10^{-3}$. Its metal-enriched emission-line properties indicate that it is already chemically evolved. These properties imply M1149-BSG-z5 as an early-assembled and structurally evolved galaxy. We also find that M1149-BSG-z5 resides in an overdense region with a nearby companion galaxy, suggesting an interaction-driven bar formation mechanism. Its concentrated light, early assembly and main-sequence star formation also suggest baryon-dominated, gas-rich conditions, where gravitational instability can further accelerate the bar formation.

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Xiaohan Wang, Fengwu Sun, Yoshihisa Asada, Yunjing Wu, Xiaojing Lin, Shude Mao, Sijia Cai, Zheng Cai, Chian-Chou Chen, Wenlei Chen, Cheng Cheng, Christopher J. Conselice, Miroslava Dessauges-Zavadsky, Daneil Espada, Brenda L. Frye, Jean-Baptiste Jolly, Anton M. Koekemoer, Kotaro Kohno, Mingyu Li, Nicholas Martis, Hideki Umehata, Weichen Wang, Rogier A. Windhorst, Adi Zitrin. 2026-06-23. A massive barred spiral galaxy at z = 5.102 discovered by JWST. https://arxiv.org/abs/2606.25022

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