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.

JWST and ALMA Discern the Assembly of Structural and Obscured Components in a High-redshift Starburst Galaxy

“…In agreement with our assessment given above, PACS-819 has kinematic properties broadly consistent with a rotating disk, which is typical for high-z star-forming galaxies (Übler et al 2018;Förster Schreiber et al 2018;Johnson et al 2018;Wisnioski et al 2019). Our conclusions align with the results presented by Rizzo et al (2023), which characterize this galaxy as rotation dominated (V rot /σ gas > 6-7) and with notable noncircular features. Such a feature can be spotted in the region pointed out by the brown arrow in Figure 9.…”

“…Such a feature can be spotted in the region pointed out by the brown arrow in Figure 9. The gas there is moving slower than the disk rotation predicted by the model, which is interpreted as inflowing or outflowing extraplanar gas in Rizzo et al (2023).…”

“…Also, there is a distinct anomaly seen in the velocity and dispersion maps at the position of the blueshifted component (Figure 7(b)) that is cospatial with the "green" JWST component in the RGB image (Figure 3) and likely indicating the existence of a distinct "clump." Rizzo et al (2023) analyze the velocity anomalies of PACS-819 in detail and conclude that these anomalies are noncircular features rotating faster or slower than the disk. These features can also be spotted on the maps constructed by our independent study, as shown by the arrow (Figure 9).…”

First Constraints on the Interstellar Medium Conditions of a Low-mass, Highly Obscured z = 4.27 Main-sequence Galaxy

“…The mass assembly of galaxies is dominated by two processes: steady cold accretion (Kereš et al 2005) and mergers (Hopkins et al 2010). While steady cold accretion tends to produce systems with stable disks (Förster Schreiber & Wuyts 2020; Rizzo et al 2023), mergers and counterrotating gas inflows may disrupt galactic structure. Generally speaking, SFGs are less likely to host rotation-dominated disks as we push to lower stellar masses and earlier epochs (Förster Schreiber & Wuyts 2020).…”

“…This is an unsurprising result; lowmass systems are easier to disrupt, and the harsher conditions of the early Universe increase the efficacy of disruptive processes (e.g., Pillepich et al 2019). However, a number of dynamically cold disks have still been observed in the highredshift regime (e.g., Rizzo et al 2020Rizzo et al , 2021Rizzo et al , 2022Rizzo et al , 2023Jones et al 2021;Roman-Oliveira et al 2023).…”