2026/06/23 by Xiaohan Wang, Fengwu Sun, Yoshihisa Asada +21 · 1 voice
Physics and Astronomy · #astro-ph.GA
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 abar ≈ 4.5 kpc, and extended spiral arms peaking at r ≈ 5.5 kpc. M1149-BSG-z5 is a massive main sequence star-forming galaxy, with a stellar mass of 1010.45\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 Sérsic index n = 2.37. With an effective radius of Re = 2.61\rm kpc, M1149-BSG-z5 is larger than typical galaxies at z ∼ 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_∗∼10-3. 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.