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arXiv · 1411.5038

Compact starbursts in z~3-6 submillimeter galaxies revealed by ALMA

Soh Ikarashi·R. J. Ivison·Karina I. Caputi·Itziar Aretxaga·James S. Dunlop·Bunyo Hatsukade·DavidH. Hughes·Daisuke Iono·Takuma Izumi·Ryohei Kawabe·Kotaro Kohno·ClaudiaD. P. Lagos·Kentaro Motohara·Koichiro Nakanishi·Kouji Ohta·Yoichi Tamura·Hideki Umehata·Grant W. Wilson·Kiyoto Yabe·Min S. Yun
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Abstract

We report the source size distribution, as measured by ALMA millimetric continuum imaging, of a sample of 13 AzTEC-selected submillimeter galaxies (SMGs) at z_photo ~ 3-6. Their infrared luminosities and star-formation rates (SFR) are L_IR ~ 2-6 x 10^12 L_sun and ~ 200-600 M_sun yr-1, respectively. The size of z ~ 3-6 SMGs ranges from 0".10 to 0".38 with a median of 0".20+0".03-0".05 (FWHM), corresponding to a median circularized effective radius (Rc,e) of 0.67+0.13-0.14 kpc, comparable to the typical size of the stellar component measured in compact quiescent galaxies at z ~ 2 (cQGs) --- R ~ 1 kpc. The median surface SFR density of our z ~ 3-6 SMGs is 100+42-26 M_sun yr-1 kpc-2, comparable to that seen in local merger-driven (U)LIRGsrather than in extended disk galaxies at low and high redshifts. The discovery of compact starbursts in z >~ 3 SMGs strongly supports a massive galaxy formation scenario wherein z ~ 3-6 SMGs evolve into the compact stellar components of z ~ 2 cQGs. These cQGs are then thought to evolve into the most massive ellipticals in the local Universe, mostly via dry mergers. Our results thus suggest that z >~ 3 SMGs are the likely progenitors of massive local ellipticals, via cQGs, meaning that we can now trace the evolutionary path of the most massive galaxies over a period encompassing ~ 90% of the age of the Universe.

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Soh Ikarashi, R. J. Ivison, Karina I. Caputi, Itziar Aretxaga, James S. Dunlop, Bunyo Hatsukade, DavidH. Hughes, Daisuke Iono, Takuma Izumi, Ryohei Kawabe, Kotaro Kohno, ClaudiaD. P. Lagos, Kentaro Motohara, Koichiro Nakanishi, Kouji Ohta, Yoichi Tamura, Hideki Umehata, Grant W. Wilson, Kiyoto Yabe, Min S. Yun. 2015-08-02. Compact starbursts in z~3-6 submillimeter galaxies revealed by ALMA. https://doi.org/10.1088/0004-637x%2F810%2F2%2F133

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