TRICEPS. I. Tracing cold gas, dust, and stars at sub-kpc scales in massive star-forming galaxies at z = 4-5

We introduce the TRICEPS (Tracing Resolved Ionized Carbon Emission in Primeval Systems) survey. TRICEPS focuses on a sample of 16 massive galaxies at z = 4 - 5 with top-quality data: (i) ALMA band-7 observations of the [CII]-158 micron line, tracing the cold gas distribution and kinematics at spatial resolutions of about 0.1" (~0.8 kpc), (ii) ALMA maps of the rest-frame 160 micron continuum emission, tracing the dust distribution at similar spatial resolutions, (iii) multi-band JWST images from NIRCam and MIRI, tracing the stellar mass distribution and star formation activity at spatial resolutions of 0.1"-0.2", and (iv) multi-line CO observations from ALMA and the VLA, including the CO(1-0) line, tracing the molecular gas content. In this first paper, we describe the TRICEPS scientific goals, the basic properties of the galaxy sample, and the ALMA band-7 observations. TRICEPS galaxies were selected based only on bright [CII] fluxes (>2 Jy km/s). They lie on the top-end of the star-forming main sequence at z = 4-5, having stellar masses between about 10^10.5-10^12 Msun and star-formation rates between about 100 - 3000 Msun/yr. To date, TRICEPS is the largest sample of galaxies at z = 4-5 for which the gas distribution and kinematics are exceptionally well resolved: on average, 46 resolution elements per galaxy with signal-to-noise ratio higher than 3. By survey design, half of the TRICEPS targets are in galaxy pairs; clear signs of tidal interactions are present in three of the four pairs. In all galaxies, the [CII] velocity fields display regular rotation, albeit the interacting galaxies tend to be somewhat more disturbed. The TRICEPS observations suggest that regular rotation is ubiquitous among massive star-forming galaxies when the Universe was less than ~1.5 Gyr old.