The ALPINE-ALMA [CII] survey: Survey strategy, observations and sample properties of 118 star-forming galaxies at $4<z<6$

O. Le Fèvre, M. Béthermin, A. Faisst, P. Capak, P. Cassata, J. D. Silverman, D. Schaerer, L. Yan

Published 2019-10-21Version 1

The ALMA-ALPINE [CII] survey (A2C2S) aims at characterizing the properties of a sample of normal star-forming galaxies (SFGs). ALPINE, the ALMA Large Program to INvestigate 118 galaxies observed in the [CII]-158$\mu$m line and far Infrared (FIR) continuum emission in the period of rapid mass assembly, right after HI reionization ended, at redshifts 4<z<6. We present the survey science goals, the observational strategy and the sample selection of the 118 galaxies observed with ALMA, with a typical beam size of about 0.7\arcsec, or $<$ 6 kpc at the median redshift of the survey. The properties of the sample are described, including spectroscopic redshifts derived from UV-rest frame, stellar masses and star-formation rates obtained from spectral energy distribution (SED) fitting. The observed properties derived from the ALMA data are presented and discussed in terms of the overall detection rate in [CII] and FIR continuum, with the observed signal-to-noise distribution. The sample is representative of the SFG population on the main sequence at these redshifts. The overall detection rate in [CII] is 64\%. From a visual inspection of the [CII] data cubes together with the large wealth of ancillary data we find a surprisingly wide range of galaxy types, including 40\% mergers, 20\% extended and dispersion dominated, 13\% compact and 11\% rotating discs, the remaining 16\% being too faint to be classified. This diversity indicates that a wide array of physical processes must be at work at this epoch, first and foremost galaxy merging. This paper sets a reference sample for the gas distribution in normal SFGs at 4<z<6, a key epoch in galaxy assembly, ideally suited for studies with future facilities like the James Webb Space Telescope and extremely large telescopes.