ALMA deep field in SSA22: Blindly detected CO emitters and [C II ] emitter candidates

Natsuki H. Hayatsu, Yuichi Matsuda, Hideki Umehata, Naoki Yoshida, Ian Smail, A. Mark Swinbank, Rob Ivison, Kotaro Kohno, Yoichi Tamura, Mariko Kubo, Daisuke Iono, Bunyo Hatsukade, Kouichiro Nakanishi, Ryohei Kawabe, Tohru Nagao, Akio K. Inoue, Tsutomu T. Takeuchi, Minju Lee, Yiping Ao, Seiji FujimotoTakuma Izumi, Yuki Yamaguchi, Soh Ikarashi, Toru Yamada

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)


We report the identification of four millimeter line-emitting galaxies with the Atacama Large Milli/submillimeter Array (ALMA) in SSA22 Field (ADF22). We analyze the ALMA 1.1-mm survey data, with an effective survey area of 5 arcmin 2, frequency ranges of 253.1-256.8 and 269.1-272.8 GHz, angular resolution of 0.″7 and rms noise of 0.8 mJy beam -1 at 36 km s -1 velocity resolution. We detect four line-emitter candidates with significance levels above 6σ. We identify one of the four sources as a CO(9-8) emitter at z = 3.1 in a member of the proto-cluster known in this field. Another line emitter with an optical counterpart is likely a CO(4-3) emitter at z = 0.7. The other two sources without any millimeter continuum or optical/near-infrared counterpart are likely to be [C ii] emitter candidates at z = 6.0 and 6.5. The equivalent widths of the [C ii] candidates are consistent with those of confirmed high-redshift [C ii] emitters and candidates, and are a factor of 10 times larger than that of the CO(9-8) emitter detected in this search. The [C ii] luminosity of the candidates are 4-7 × 10 8 L ⊙. The star formation rates (SFRs) of these sources are estimated to be 10-20 M ⊙ yr -1 if we adopt an empirical [C ii] luminosity-SFR relation. One of them has a relatively low S/N ratio, but shows features characteristic of emission lines. Assuming that at least one of the two candidates is a [C ii] emitter, we derive a lower limit of [C ii]-based star formation rate density (SFRD) at z ∼ 6. The resulting value of >10 -2 M ⊙ yr -1 Mpc -3 is consistent with the dust-uncorrected UV-based SFRD. Future millimeter/submillimeter surveys can be used to detect a number of high-redshift line emitters, with which to study the star formation history in the early universe.

Original languageEnglish
Article number45
JournalPublications of the Astronomical Society of Japan
Issue number3
Publication statusPublished - 2017 Jun 1
Externally publishedYes


  • early universe
  • galaxies: clusters: individual (SSA22)
  • galaxies: formation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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