Ken Ichi Tadaki, Reinhard Genzel, Tadayuki Kodama, Stijn Wuyts, Emily Wisnioski, Natascha M.Förster Schreiber, Andreas Burkert, Philipp Lang, Linda J. Tacconi, Dieter Lutz, Sirio Belli, Richard I. Davies, Bunyo Hatsukade, Masao Hayashi, Rodrigo Herrera-Camus, Soh Ikarashi, Shigeki Inoue, Kotaro Kohno, Yusei Koyama, J. Trevor MendelKouichiro Nakanishi, Rhythm Shimakawa, Tomoko L. Suzuki, Yoichi Tamura, Ichi Tanaka, Hannah Übler, Dave J. Wilman

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95 Citations (Scopus)


We present 0.″2-resolution Atacama Large Millimeter/submillimeter Array observations at 870 μm for 25 Hα-seleced star-forming galaxies around the main sequence at z = 2.2-2.5. We detect significant 870 μm continuum emission in 16 (64%) of these galaxies. The high-resolution maps reveal that the dust emission is mostly radiated from a single region close to the galaxy center. Exploiting the visibility data taken over a wide uv distance range, we measure the half-light radii of the rest-frame far-infrared emission for the best sample of 12 massive galaxies with log(M /M o) > 11. We find nine galaxies to be associated with extremely compact dust emission with R 1/2,870 μm < 1.5 kpc, which is more than a factor of 2 smaller than their rest-optical sizes, , and is comparable with optical sizes of massive quiescent galaxies at similar redshifts. As they have an exponential disk with Sérsic index of in the rest-optical, they are likely to be in the transition phase from extended disks to compact spheroids. Given their high star formation rate surface densities within the central 1 kpc of M o yr-1 kpc-2, the intense circumnuclear starbursts can rapidly build up a central bulge with ΣM ∗,1 kpc > 1010 M o kpc-2 in several hundred megayears, i.e., by z ∼ 2. Moreover, ionized gas kinematics reveal that they are rotation supported with an angular momentum as large as that of typical star-forming galaxies at z = 1-3. Our results suggest that bulges are commonly formed in extended rotating disks by internal processes, not involving major mergers.

Original languageEnglish
Article number135
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 2017 Jan 10


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