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arXiv · 2510.18006

Formation of Substructure in Luminous Submillimeter Galaxies (FOSSILS): Evidence of Multiple Pathways to Trigger Starbursts in Luminous Submillimeter Galaxies

Ryota Ikeda·Daisuke Iono·Ken-ichi Tadaki·Maximilien Franco·Min S. Yun·Jorge A. Zavala·Yoichi Tamura·Takafumi Tsukui·Christina C. Williams·Bunyo Hatsukade·Minju M. Lee·Tomonari Michiyama·Ikki Mitsuhashi·Kouichiro Nakanishi·Caitlin M. Casey·Soh Ikarashi·Kianhong Lee·Yuichi Matsuda·Toshiki Saito·Andrea Silva·Hideki Umehata·Hidenobu Yajima
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Abstract

We present an analysis of rest-frame optical and far-infrared continuum emission in three luminous submillimeter galaxies (SMGs) at $3.0\lesssim z\lesssim4.5$. The SMGs are spatially resolved down to 400-500 pc (0.05'') resolution by James Webb Space telescope (JWST) and Atacama Large Millimeter/submillimeter Array (ALMA) observations. Despite similarities in their observed far-infrared properties (flux density, infrared luminosity, and effective radius), the three SMGs exhibit heterogeneous morphologies both across wavelengths and among the sources themselves. While two of them (AzTEC-4 and AzTEC-8) show a disk-like structure in optical continuum, AzTEC-1 is dominated by highly concentrated component with the Sersic index of $n=5.4$, where its far-infrared continuum emission is clumpy and less concentrated. AzTEC-4, which is confirmed to be at $z=4.198$, shows a two-arm spiral of dust, but not in the stellar distribution. These three SMGs exemplify that multiple physical mechanisms exist in triggering starbursts in luminous SMGs at high redshift: secular instability in gas disks (AzTEC-4) in addition to possible minor mergers (AzTEC-8), and a combination of the efficient gas supply to the central core induced by a gas-rich major merger and the reformation of cold gas disk (AzTEC-1).

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Ryota Ikeda, Daisuke Iono, Ken-ichi Tadaki, Maximilien Franco, Min S. Yun, Jorge A. Zavala, Yoichi Tamura, Takafumi Tsukui, Christina C. Williams, Bunyo Hatsukade, Minju M. Lee, Tomonari Michiyama, Ikki Mitsuhashi, Kouichiro Nakanishi, Caitlin M. Casey, Soh Ikarashi, Kianhong Lee, Yuichi Matsuda, Toshiki Saito, Andrea Silva, Hideki Umehata, Hidenobu Yajima. 2025-10-20. Formation of Substructure in Luminous Submillimeter Galaxies (FOSSILS): Evidence of Multiple Pathways to Trigger Starbursts in Luminous Submillimeter Galaxies. https://doi.org/10.3847/1538-4357%2Fae157e

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