Faint end of 1.3 mm number counts revealed by alma

Bunyo Hatsukade, Kouji Ohta, Akifumi Seko, Kiyoto Yabe, Masayuki Akiyama

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59 Citations (Scopus)


We present the faint end of number counts at 1.3 mm (238 GHz) obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). Band 6 observations were carried out targeting 20 star-forming galaxies at z ∼ 1.4 in the Subaru/XMM-Newton Deep Survey field. In the observations, we serendipitously detect 15 sources (≥3.8σ, S 1.3 mm = 0.15-0.61 mJy) other than the targeted sources. We create number counts by using these "sub-mJy sources," which probe the faintest flux range among surveys at millimeter wavelengths. The number counts are consistent with (flux-scaled) number counts at 850 μm and 870 μm obtained with gravitational lensing clusters. The ALMA number counts agree well with model predictions, which suggest that these sub-mJy populations are more like "normal" star-forming galaxies than "classical" submillimeter galaxies with intense star-forming activity. In this flux range, ∼80% of the extragalactic background light at 1.3 mm is resolved into individual sources.

Original languageEnglish
Article numberL27
JournalAstrophysical Journal Letters
Issue number2
Publication statusPublished - 2013 Jun 1


  • cosmology: observations
  • galaxies: ISM
  • galaxies: evolution
  • galaxies: formation
  • galaxies: high-redshift


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