The central structure in three of the brightest unlensed z=3-4 submillimeter galaxies are investigated through 0.015" - 0.05" (120 -- 360~pc) 860 micron continuum images obtained using the Atacama Large Millimeter/submillimeter Array (ALMA). The distribution in the central kpc in AzTEC1 and AzTEC8 are extremely complex, and they are composed of multiple ~200 pc clumps. AzTEC4 consists of two sources that are separated by ~1.5 kpc, indicating a mid-stage merger. The peak star formation rate densities in the central clumps are ~300 - 3000 Msun/yr/kpc^2, suggesting regions with extreme star formation near the Eddington Limit. By comparing the flux obtained by ALMA and Submillimeter Array (SMA), we find that 68-90% of the emission is extended (> 1 kpc) in AzTEC 4 and 8. For AzTEC1, we identify at least 11 additional compact (~200 pc) clumps in the extended 3 - 4 kpc region. Overall, the data presented here suggest that the luminosity surface densities observed at < 150 pc scales are roughly similar to that observed in local ULIRGs, as in the eastern nucleus of Arp 220. Between 10 to 30% of the 860 micron continuum is concentrated in clumpy structures in the central kpc while the remaining flux is distributed over > 1 kpc regions, some of which could also be clumpy. These sources can be explained by a rapid inflow of gas such as a merger of gas-rich galaxies, surrounded by extended and clumpy starbursts. However, the cold mode accretion model is not ruled out.
@article{arxiv.1609.02365,
title = {Clumpy and Extended Starbursts in the Brightest Unlensed Submillimeter Galaxies},
author = {Daisuke Iono and Min S. Yun and Itziar Aretxaga and Bunyo Hatsukade and David Hughes and Soh Ikarashi and Takuma Izumi and Ryohei Kawabe and Kotaro Kohno and Minju Lee and Yuichi Matsuda and Kouichiro Nakanishi and Toshiki Saito and Yoichi Tamura and Junko Ueda and Hideki Umehata and Grant Wilson and Tomonari Michiyama and Misaki Ando},
journal= {arXiv preprint arXiv:1609.02365},
year = {2016}
}