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Department of Physics

# Staff profile

## Publication details for Prof David Alexander

Umehata, H., Tamura, Y., Kohno, K., Ivison, R.J., Smail, I., Hatsukade, B., Nakanishi, K., Kato, Y., Ikarashi, S., Matsuda, Y., Fujimoto, S., Iono, D., Lee, M., Steidel, C.C., Saito, T., Alexander, D.M., Yun, M.S. & Kubo, M. (2017). ALMA Deep Field in SSA22: Source Catalog and Number Counts. The Astrophysical Journal 835(1): 98.

### Abstract

We present results from a deep 2' × 3' (comoving scale of 3.7 Mpc × 5.5 Mpc at z = 3) survey at 1.1 mm, taken with the Atacama Large Millimeter/submillimeter Array (ALMA) in the SSA22 field. We observe the core region of a z = 3.09 protocluster, achieving a typical rms sensitivity of 60 μJy beam−1 at a spatial resolution of 0farcs7. We detect 18 robust ALMA sources at a signal-to-noise ratio (S/N) > 5. Comparison between the ALMA map and a 1.1 mm map, taken with the AzTEC camera on the Atacama Submillimeter Telescope Experiment (ASTE), indicates that three submillimeter sources discovered by the AzTEC/ASTE survey are resolved into eight individual submillimeter galaxies (SMGs) by ALMA. At least 10 of our 18 ALMA SMGs have spectroscopic redshifts of z sime 3.09, placing them in the protocluster. This shows that a number of dusty starburst galaxies are forming simultaneously in the core of the protocluster. The nine brightest ALMA SMGs with S/N > 10 have a median intrinsic angular size of $0\buildrel{\prime\prime}\over{.} {32}_{-0.06}^{+0.13}$ (${2.4}_{-0.4}^{+1.0}$ physical kpc at z = 3.09), which is consistent with previous size measurements of SMGs in other fields. As expected, the source counts show a possible excess compared to the counts in the general fields at S1.1mm ≥ 1.0 mJy, due to the protocluster. Our contiguous mm mapping highlights the importance of large-scale structures on the formation of dusty starburst galaxies.