The ALMA Patchy Deep Survey: A blind search for [C II] emitters at z ~ 4.5

Abstract

We present a result of a blind search for [C II] 158 μm emitters at z ~ 4.5 using Atacama Large Millimeter Array (ALMA) Cycle 0 archival data. We collected extragalactic data covering at 330-360 GHz (band 7) from 8 Cycle 0 projects from which initial results have been already published. The total number of fields is 243 and the total on-source exposure time is 19.2 h. We searched for line emitters in continuum-subtracted data cubes with spectral resolutions of ~50, 100, 300 and 500 km s-1.We could not detect any new line emitters above a 6σ significance level. This result provides upper limits to the [C II] luminosity function at z ~ 4.5 over L[C II] ~ 108-1010 L⊙ or star formation rate, SFR ~ 10-1000 M⊙yr-1. These limits are at least two orders of magnitude larger than the [C II] luminosity functions expected from the z ~ 4 UV luminosity function or from numerical simulation. However, this study demonstrates that we would be able to better constrain the [C II] luminosity function and to investigate possible contributions from dusty galaxies to the cosmic star formation rate density by collecting Cycle 1+2 archival data as the ALMA Patchy Deep Survey.