exoALMA XXII: A Two-dimensional Atlas of Deviations from Keplerian Disks

Abstract

Protoplanetary disks are the birthplaces of planetary systems, and deviations from Keplerian rotation imprinted in disk gas kinematics serve as key tracers of physical processes and the presence of protoplanets within disks. Using the the CO (J=3-2) data from the exoALMA Large Program encompassing 15 disks, we constructed two-dimensional (2D) maps of centroid velocity, line width, and peak intensity, and extracted non-Keplerian deviations by subtracting smooth Keplerian models. This paper provides the first systematic and uniform overview of 2D gas substructures across the entire exoALMA sample. We find that all targets exhibit large-scale deviations from smooth Keplerian disks, displaying a variety of morphologies including spiral-like structures, arc- or ring-like features, and patterns indicative of variations in the emitting surface height. Non-axisymmetric spiral-arm features are detected or suggested in five disks (CQ Tau, MWC 758, HD 135344B, HD 34282, and SY Cha), and are preferentially found in Herbig Ae/Fe systems. In contrast, some other sources (J1852, PDS 66, and V4046 Sgr), despite exhibiting noticeable deviations, appear to be dynamically quieter. This 2D atlas suggests that kinematic substructures are ubiquitous in large ($\gtrsim$ 100 au) protoplanetary disks with ages of a few million years, based on the observations obtained with sufficient sensitivity at moderate-to-high spatial resolution of $\sim$20 au and high velocity resolution of $\sim$0.1 km s$^{-1}$.

Figures (8)

• Figure 1: Velocity (line centroid) images in $^{12}$CO (3--2) obtained with discminer. All panels are shown using a common color scale, as indicated by the color bar on the right. The beam size is the same at $0\hbox{$.\!\!^{\prime\prime}$}15$ for all the sources and is indicated in the lower left corner of each panel, though the panel size varies. The black line shown in the lower right corner of each panel represents a spatial scale of 100 au. Pixels with S/N below 4.5 are masked. The major and minor axes of the fitted disk model are shown as black dashed lines. The emitting surfaces are overlaid as thin gray contours at radial intervals corresponding to integer multiples of the beam size (1--4 beams, depending on the panel), chosen to avoid overcrowding.
• Figure 2: The same as Figure \ref{['fig:velocity_12co']} but for the line width. Pixels with S/N below 4.5 are masked.
• Figure 3: The same as Figure \ref{['fig:velocity_12co']} but for the peak intensity. Pixels with S/N below 4 are masked.
• Figure 4: Residual centroid-velocity images of the $^{12}$CO (3-2) emission after subtracting the fitted disk model cube. The definition of lines and beam-size indication are the same as Figure \ref{['fig:velocity_12co']}. Pixels with S/N below 4.5 are masked. The yellow, purple, and green arrows indicate the spiral features (Section \ref{['sec:spiral_vres']}), the quadrupole pattern (Section \ref{['sec:other_quadrupole']}), and the red-shifted arc (Section \ref{['sec:arcs_combined']}), respectively. The letter in the upper-left corner of each panel indicates the classification defined in Section 3.2: “S” for spiral, “A” for arcs/rings, and “O” for other types. Labels in parentheses indicate features that appear to be present but are ambiguous.
• Figure 5: The same as Figure \ref{['fig:velocity_res']} but for the line width. Pixels with S/N below 4.5 are masked.