The ALMA-ALPAKA survey

I. High-resolution CO and [CI] kinematics of star-forming galaxies at z = 0.5–3.5

¹ Cosmic Dawn Center (DAWN), Jagtvej 128, 2200 Copenhagen N, Denmark
² Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen N, Denmark
e-mail: francesca.rizzo@nbi.ku.dk
³ Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
⁴ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
⁵ Istituto Nazionale di Astrofisica, Vicolo dell’Osservatorio 5, 35122, Padova, Italy
⁶ Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003, USA
⁷ Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
⁸ DTU-Space, Technical University of Denmark, Elektrovej 327, 2800 Kgs. Lyngby, Denmark
⁹ Astronomy Unit, Department of Physics, University of Trieste, via Tiepolo 11, Trieste 34131, Italy
¹⁰ INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, Trieste 34131, Italy
¹¹ IFPU – Institute for Fundamental Physics of the Universe, Via Beirut 2, 34014 Trieste, Italy
¹² Department of Astronomy, School of Science, SOKENDAI (The Graduate University for Advanced Studies), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹³ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan

Received: 17 March 2023
Accepted: 7 August 2023

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.