The ALMA-ALPAKA survey

Abstract

Context. Spatially resolved studies of the kinematics of galaxies provide crucial insights into their assembly and evolution, enabling one to infer the properties of the dark matter halos, derive the impact of feedback on the interstellar medium (ISM), as well as measure and characterize the outflow motions. To date, most of the kinematic studies at z = 0.5 − 3.5 have been obtained using emission lines tracing the warm, ionized gas (e.g., Hα, [OII], and [OIII]). However, whether these provide an exhaustive or only a partial view of the dynamics of galaxies and of the properties of the ISM is still debated. Complementary insights into the cold gas kinematics are therefore needed. Aims. We present the Archival Large Program to Advance Kinematic Analysis (ALPAKA), a project aimed at gathering high-resolution observations of CO and [CI] emission lines of star-forming galaxies at z = 0.5 − 3.5 from the Atacama Large Millimeter Array (ALMA) public archive. With ≈147 h of total integration time, ALPAKA assembles ∼0.25″ observations for 28 star-forming galaxies, which is the largest sample with spatially resolved cold gas kinematics as traced by either CO or [CI] at z ≳ 0.5, spanning 7 Gyr of cosmic history. A large fraction of ALPAKA galaxies (19 out of 28) lie in overdense regions (clusters, groups, and protoclusters). Methods. By combining multiwavelength ground- and space-based ancillary data, we derived the stellar masses (M⋆) and star-formation rates (SFRs) for the ALPAKA targets. We exploited the ALMA data to infer the dynamical state of the ALPAKA galaxies and derive their rotation curves and velocity dispersion profiles using 3DBAROLO. Results. ALPAKA probes the massive (M⋆ ≳ 1010 M⊙), actively star-forming (SFR ≈ 10 − 3000 M⊙ yr−1) part of the population of galaxies at z ∼ 0.5 − 3.5. Based on our kinematic classification, we find that 19 out of 28 ALPAKA galaxies are rotating disks, two are interacting systems, while for the remaining seven sources the classification is uncertain. The disks have velocity dispersion values that are typically larger in the innermost regions than in the outskirts, with a median value for the entire disk sample of 35−9+11 km s−1. Despite the bias of our sample toward galaxies hosting very energetic mechanisms, the ALPAKA disks have high ratios of ordered-to-random motion (V/σ) with a median value of 9−2+7.