RIOJA. Complex Dusty Starbursts in a Major Merger B14-65666 at z = 7.15
Costantin, Luca;
Arribas, Santiago;
Inoue, Akio K.;
Hashimoto, Takuya;
Sugahara, Yuma;
Tamura, Yoichi;
Marques-Chaves, Rui;
Colina, Luis;
Álvarez-Márquez, Javier;
Pereira-Santaella, Miguel;
Fudamoto, Yoshinobu;
Mawatari, Ken;
Matsuo, Hiroshi;
Bakx, Tom J. L. C.;
Yoshida, Naoki;
Hagimoto, Masato;
Nakazato, Yurina;
Ceverino, Daniel;
Usui, Mitsutaka;
Ren, Yi W.;
Blanco-Prieto, Carmen;
Crespo Gómez, Alejandro;
Hashigaya, Takeshi
Japan, Spain, Sweden, Switzerland
Abstract
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 (βUV = ‑2.2 ± 0.1). The flux excess, F356W ‑ F444W, peaks at the E-core ( mag), tracing the presence of strong [O III] λλ4960,5008 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 μm. 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, ≃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 βUV diagram. The high optical-to-far-IR [O III] line ratio of the E-core shows its lower gas-phase metallicity (≃0.2–0.4 Z⊙) 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.
2025
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The Astrophysical Journal
Gaia
5
