RIOJA. Complex Dusty Starbursts in a Major Merger B14-65666 at z=7.15
Journal article, 2025
We present JWST NIRCam imaging of B14-65666 ("Big Three Dragons"), a bright Lyman-break galaxy system (MUV = -22.5 mag) at z = 7.15. The high angular resolution of NIRCam reveals the complex morphology of two galaxy components: galaxy E has a compact core (E-core), surrounded by diffuse, extended, rest-frame optical emission, which is likely to be tidal tails; and galaxy W has a clumpy and elongated morphology with a blue UV slope (beta UV = -2.2 +/- 0.1). The flux excess, F356W - F444W, peaks at the E-core ( 1.05-0.09+0.08 mag), tracing the presence of strong [O iii] lambda lambda 4960,5008 emission. Atacama Large Millimeter/submillimeter Array archival data show that the bluer galaxy W is brighter in dust continua than the redder galaxy E, while the tails are bright in [O iii] 88 mu m. The UV/optical and submillimeter spectral energy distribution (SED) fitting confirms that B14-65666 is a major merger in a starburst phase as derived from the stellar mass ratio (3:1 to 2:1) and the star formation rate, similar or equal to 1 dex higher than the star formation main sequence at the same redshift. Galaxy E is a dusty (AV = 1.2 +/- 0.1 mag) starburst with a possible high dust temperature (>= 63-68 K). Galaxy W would have a low dust temperature (<= 27-33 K) or patchy stellar-and-dust geometry, as suggested by the IR excess and beta UV diagram. The high optical-to-far-IR [O iii] line ratio of the E-core shows its lower gas-phase metallicity (similar or equal to 0.2-0.4 Z circle dot) than galaxy W. These results agree with a scenario where major mergers disturb morphology and induce nuclear dusty starbursts triggered by less-enriched inflows. B14-65666 shows a picture of complex stellar buildup processes during major mergers in the epoch of reionization.
Star-forming galaxy
Stellar feedback
Luminosity function
Ionized-gas
Mass-metallicity relation
Infrared-emission
Lyman-break galaxy
High-redshift
Line ratios
Big 3 dragons
Author
Yuma Sugahara
Waseda University
National Astronomical Observatory of Japan
Javier Álvarez-Márquez
Spanish National Research Council (CSIC)
Takuya Hashimoto
University of Tsukuba
Luis Colina
Spanish National Research Council (CSIC)
Akio K. Inoue
Waseda University
Luca Constantin
Spanish National Research Council (CSIC)
Yoshinobu Fudamoto
Chiba University
National Astronomical Observatory of Japan
Waseda University
Ken Mawatari
University of Tsukuba
Yi W. Ren
Waseda University
Santiago Arribas
Spanish National Research Council (CSIC)
Tom Bakx
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Carmen Blanco-Prieto
Spanish National Research Council (CSIC)
Daniel Ceverino
Universidad Autonoma de Madrid (UAM)
Alejandro Crespo Gomez
Spanish National Research Council (CSIC)
Masato Hagimoto
Nagoya University
Takeshi Hashigaya
Kyoto University
Rui Marques-Chaves
University of Geneva
Hiroshi Matsuo
National Astronomical Observatory of Japan
The Graduate University for Advanced Studies (SOKENDAI)
Yurina Nakazato
University of Tokyo
Miguel Pereira-Santaella
Spanish National Research Council (CSIC)
Yoichi Tamura
Nagoya University
Mitsutaka Usui
University of Tsukuba
Naoki Yoshida
University of Tokyo
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 981 2 135Subject Categories (SSIF 2025)
Astronomy, Astrophysics, and Cosmology
DOI
10.3847/1538-4357/adb02a