SXDF-ALMA 1.5 arcmin2 Deep Survey: A Compact Dusty Star-forming Galaxy at z = 2.5
Tamura, Yoichi; Kohno, Kotaro; Caputi, Karina I.; Yun, Min S.; Koyama, Yusei; Kodama, Tadayuki; Hayashi, Masao; Tadaki, Ken-ichi; Berta, Stefano; Wuyts, Stijn; Yamaguchi, Yuki; Hatsukade, Bunyo; Dunlop, James S.; Rujopakarn, Wiphu; Wang, Wei-Hao; Izumi, Takuma; Wilson, Grant W.; Hughes, David H.; Aretxaga, Itziar; Lutz, Dieter; Nakanishi, Kouichiro; Umehata, Hideki; Matsuda, Yuichi; Ikarashi, Soh; Ivison, Rob; Makiya, Ryu
Germany, Japan, Netherlands, Mexico, United Kingdom, Chile, Thailand, Taiwan, United States
Abstract
We present the first results from the SXDF-Atacama Large Millimeter/submillimeter Array (ALMA) 1.5 arcmin2 deep survey at 1.1 mm using ALMA. The map reaches a 1σ depth of 55 μJy/beam and covers 12 Hα-selected star-forming galaxies (SFGs) at z = 2.19 or z = 2.53. We have detected continuum emission from three of our Hα-selected sample, including one compact SFG with high stellar surface density, NB2315-07. They are all red in the rest-frame optical and have stellar masses of log (M*/M⊙) > 10.9, whereas the other blue, main-sequence galaxies with {log}({M}*/{M}⊙ ) = 10.0-10.8 are exceedingly faint, <290 μJy (2σ upper limit). We also find the 1.1 mm brightest galaxy, NB2315-02, to be associated with a compact (Re = 0.7 ± 0.1 kpc), dusty star-forming component. Given a high gas fraction ({44}-8+20% or {37}-3+25%) and high star formation rate surface density ({126}-30+27{M}⊙ yr-1 kpc-2), the concentrated starburst can build up within less than {50}-11+12 Myr a stellar surface density matching that of massive compact galaxies at z ∼ 2, provided at least 19 ± 3% of the total gas is converted into stars in the galaxy center. On the other hand, NB2315-07, which already has such a high stellar surface density core, shows a gas fraction ({23}-8+8%) and is located in the lower envelope of the star formation main sequence. This compact, less SFG is likely to be in an intermediate phase between compact, dusty star-forming and quiescent galaxies.