Sazuna/UAT_keywords huggingface dataset:
exoALMA. VII. Benchmarking Hydrodynamics and Radiative Transfer Codes. Forward modeling is often used to interpret substructures observed in protoplanetary disks. To ensure the robustness and consistency of the current forward-modeling approach from the community, we conducted a systematic comparison of various hydrodynamics and radiative transfer codes. Using four grid-based hydrodynamics codes (FARGO3D, Idefix, Athena++, and PLUTO) and a smoothed-particle hydrodynamics code (Phantom), we simulated a protoplanetary disk with an embedded giant planet. We then used two radiative transfer codes (mcfost and RADMC-3D) to calculate disk temperatures and create synthetic 12CO cubes. Finally, we retrieved the location of the planet from the synthetic cubes using DISCMINER. We found strong consistency between the hydrodynamics codes, particularly in the density and velocity perturbations associated with planet-driven spirals. We also found a good agreement between the two radiative transfer codes: the disk temperature in mcfost and RADMC-3D models agrees within ≲3% everywhere in the domain. In synthetic 12CO channel maps, this results in brightness temperature differences within ±1.5 K in all our models. This good agreement ensures consistent retrieval of planet's radial/azimuthal location with only a few percent of scatter, with velocity perturbations varying ≲20% among the models. Notably, while the planet-opened gap is shallower in the Phantom simulation, we found that this does not impact the planet location retrieval. In summary, our results demonstrate that any combination of the tested hydrodynamics and radiative transfer codes can be used to reliably model and interpret planet-driven kinematic perturbations.

Keywords: Hydrodynamical simulations, Radiative transfer simulations, Planetary-disk interactions, Protoplanetary disks
exoALMA. VIII. Probabilistic Moment Maps and Data Products Using Nonparametric Linear Models. Extracting robust inferences on physical quantities from disk kinematics measured from Doppler-shifted molecular line emission is challenging due to the data's size and complexity. In this paper, we develop a flexible linear model of the intensity distribution in each frequency channel, accounting for spatial correlations from the point-spread function. The analytic form of the model's posterior enables probabilistic data products through sampling. Our method debiases peak intensity, peak velocity, and line width maps, particularly in disk substructures that are only partially resolved. These are needed in order to measure disk mass, turbulence, and pressure gradients and detect embedded planets. We analyze HD 135344B, MWC 758, and CQ Tau, finding velocity substructures 50–200 m s‑1 greater than with conventional methods. Additionally, we combine our approach with DISCMINER in a case study of J1842. We find that uncertainties in stellar mass and inclination increase by an order of magnitude due to the more realistic noise model. More broadly, our method can be applied to any problem requiring a probabilistic model of an intensity distribution conditioned on a point-spread function.

Keywords: Nonparametric inference, Astronomy data modeling, Planetary-disk interactions, Protoplanetary disks, Linear regression, Radio interferometry, Planet formation
exoALMA. IX. Regularized Maximum Likelihood Imaging of Non-Keplerian Features. The planet-hunting Atacama Large Millimeter/submillimeter Array (ALMA) large program exoALMA observed 15 protoplanetary disks at   angular resolution and ∼100 m s−1 spectral resolution, characterizing disk structures and kinematics in enough detail to detect non-Keplerian features (NKFs) in the gas emission. As these features are often small and low-contrast, robust imaging procedures are critical for identifying and characterizing NKFs, including determining which features may be signatures of young planets. The exoALMA collaboration employed two different imaging procedures to ensure the consistent detection of NKFs: CLEAN, the standard iterative deconvolution algorithm, and regularized maximum likelihood (RML) imaging. This Letter presents the exoALMA RML images, obtained by maximizing the likelihood of the visibility data given a model image and subject to regularizer penalties. Crucially, in the context of exoALMA, RML images serve as an independent verification of marginal features seen in the fiducial CLEAN images. However, best practices for synthesizing RML images of multichanneled (i.e., velocity-resolved) data remain undefined, as prior work on RML imaging for protoplanetary disk data has primarily addressed single-image cases. We used the open-source Python package MPoL to explore RML image validation methods for multichanneled data and synthesize RML images from the exoALMA observations of seven protoplanetary disks with apparent NKFs in the 12CO J = 3─2 CLEAN images. We find that RML imaging methods independently reproduce the NKFs seen in the CLEAN images of these sources, suggesting that the NKFs are robust features rather than artifacts from a specific imaging procedure.

Keywords: Deconvolution, Computational methods, Protoplanetary disks, Submillimeter astronomy, Planet formation
exoALMA. X. Channel Maps Reveal Complex <SUP>12</SUP>CO Abundance Distributions and a Variety of Kinematic Structures with Evidence for Embedded Planets. We analyze the 12CO J = 3─2 data cubes of the disks in the exoALMA program. 13/15 disks reveal a variety of kinematic substructures in individual channels: large-scale arcs or spiral arms, localized velocity kinks, and/or multiple faints arcs that appear like filamentary structures on the disk surface. We find kinematic signatures that are consistent with planet wakes in six disks: AA Tau, SY Cha, J1842, J1615, LkCa 15, and HD 143006. Comparison with hydrodynamical and radiative transfer simulations suggests planets with orbital radii between 80 and 310 au and masses between 1 and 5 MJup. Additional kinematic substructures limit our ability to place tight constraints on the planet masses. When the inclination is favorable to separate the upper and lower surfaces (near 45°, i.e., in 7/15 disks), we always detect the vertical CO snowline and find that the 12CO freeze-out is partial in the disk midplane, with a depletion factor of ≍10−3 ─10−2 compared to the warm molecular layer. In these same seven disks, we also systematically detect evidence of CO desorption in the outer regions.

Keywords: Planetary-disk interactions, Hydrodynamics, Exoplanets, Protoplanetary disks, Radiative transfer, Submillimeter astronomy, Exoplanet formation
exoALMA. XI. ALMA Observations and Hydrodynamic Models of LkCa 15: Implications for Planetary Mass Companions in the Dust Continuum Cavity. In the past decade, the Atacama Large Millimeter/submillimeter Array (ALMA) has revealed a plethora of substructures in the disks surrounding young stars. These substructures have several proposed formation mechanisms, with one leading theory being the interaction between the disk and newly formed planets. In this Letter, we present high angular resolution ALMA observations of LkCa 15's disk that reveal a striking difference in dust and CO emission morphology. The dust continuum emission shows a ringlike structure characterized by a dust-depleted inner region of ∼40 au in radius. Conversely, the CO emission is radially smoother and shows no sign of gas depletion within the dust cavity. We compare the observations with models for the disk–planet interaction, including radiative transfer calculation in the dust and CO emission. This source is particularly interesting, as the presence of massive planets within the dust cavity has been suggested based on previous near-IR observations. We find that the level of CO emission observed within the dust cavity is inconsistent with the presence of planets more massive than Jupiter orbiting between 10 and 40 au. Instead, we argue that the LkCa 15 innermost dust cavity might be created either by a chain of low-mass planets or by other processes that do not require the presence of planets.

Keywords: Hydrodynamical simulations, Circumstellar matter, Protoplanetary disks, Radiative transfer simulations, Planet formation, Circumstellar gas
exoALMA. XII. Weighing and Sizing exoALMA Disks with Rotation Curve Modelling. The exoALMA large program offers a unique opportunity to investigate the fundamental properties of protoplanetary disks, such as their masses and sizes, providing important insights into the mechanism responsible for the transport of angular momentum. In this work, we model the rotation curves of CO isotopologues 12CO and 13CO of 10 sources within the exoALMA sample, and we constrain the stellar mass, the disk mass, and the density scale radius through precise characterization of the pressure gradient and disk self-gravity. We obtain dynamical disk masses for our sample by measuring the self-gravitating contribution to the gravitational potential. We are able to parametrically describe their surface density, and all of them appear gravitationally stable. By combining dynamical disk masses with dust continuum emission data, we determine an averaged gas-to-dust ratio of approximately 400, not statistically consistent with the standard value of 100, assuming optically thin dust emission. In addition, the measurement of the dynamical scale radius allows for direct comparison with flux-based radii of gas and dust. This comparison suggests that substructures may influence the size of the dust disk and that CO depletion might reconcile our measurements with thermochemical models. Finally, with the stellar mass, disk mass, scale radius, and accretion rate, and assuming self-similar evolution of the surface density, we constrain the effective αS for these systems. We find a broad range of αS values ranging between 10‑5 and 10‑2.

Keywords: Stellar accretion disks, Protoplanetary disks, Planet formation
exoALMA. XIII. Gas Masses from N<SUB>2</SUB>H<SUP>+</SUP> and C<SUP>18</SUP>O: A Comparison of Measurement Techniques for Protoplanetary Gas Disk Masses. The gas masses of protoplanetary disks are important but elusive quantities. In this work we present new Atacama Large Millimeter/submillimeter Array (ALMA) observations of N2H+ (3─2) for 11 exoALMA disks. N2H+ is a molecule sensitive to CO freeze-out and has recently been shown to significantly improve the accuracy of gas masses estimated from CO line emission. We combine these new observations with archival N2H+ and CO isotopologue observations to measure gas masses for 19 disks, predominantly from the exoALMA large program. For 15 of these disks the gas mass has also been measured using gas rotation curves. We show that the CO + N2H+ line emission-based gas masses typically agree with the kinematically measured ones within a factor of 3 (∼1σ─2σ). Gas disk masses from CO + N2H+ are on average a factor of   lower than the kinematic disk masses, which could suggest slightly lower N2 abundances and/or lower midplane ionization rates than typically assumed. Herbig disks are found to have CO gas abundances at the level of the interstellar medium based on their CO and N2H+ fluxes, which sets them apart from T Tauri disks, where abundances are typically ∼3−30× lower. The agreement between CO + N2H+-based and kinematically measured gas masses is promising and shows that multimolecule line fluxes are a robust tool to accurately measure disk masses at least for extended disks.

Keywords: Interferometry, Radio interferometry, Protoplanetary disks, Astrochemistry
exoALMA. XIV. Gas Surface Densities in the RX J1604.3‑2130 A Disk from Pressure-broadened CO Line Wings. Gas surface density is one of the most relevant physical quantities in protoplanetary disks. However, its precise measurement remains highly challenging due to the lack of a direct tracer. In this study, we report the spatially resolved detection of pressure-broadened line wings in the CO J = 3–2 line in the RX J1604.3‑2130 A transition disk as part of the exoALMA large program. Since pressure-broadened line wings are sensitive to the total gas volume density, we robustly constrain the radial dependence of the gas surface density and midplane pressure in the region located 50–110 au from the central star, which encompasses the dust ring of the system. The peak radius of the midplane pressure profile matches the dust ring radial location, directly proving radial dust trapping at a gas pressure maximum. The peak gas surface density is 18–44 g cm‑2 and decreases at radii interior to and exterior of the dust ring. A comparison of the gas and dust surface densities suggests that the disk turbulence is as low as αturb ∼ 2 × 10‑4. Despite dust trapping, the gas-to-dust surface density ratio at the ring peak is 70–400, which implies already-formed protoplanets and/or less efficient dust trapping. The gas surface density drop at radii interior to the ring is consistent with a gas gap induced by a Jupiter-mass planet. The total gas mass within 50 &lt; r &lt; 110 au is estimated to be ∼0.05–0.1 M⊙(50–100 MJup), suggesting that planetary system formation is possible.

Keywords: Protoplanetary disks, Planet formation
exoALMA. XV. Interpreting the Height of CO Emission Layer. The availability of exquisite data and the development of new analysis techniques have enabled the study of emitting heights in protoplanetary disks. In this paper, we introduce a simple model linking the emitting height of CO to the disk surface density and temperature structure. We then apply the model to measurements of the emitting height and disk temperature conducted as part of exoALMA, integrated with additional legacy measurements from the MAPS Large Programme, to derive CO column densities and surface density profiles (assuming a CO abundance) for a total of 14 disks. A unique feature of the method we introduce to measure surface densities is that it can be applied to optically thick observations, rather than optically thin as conventionally done. While we use our method on a sample of well-studied disks where temperature structures have been derived using two emission lines, we show that reasonably accurate estimates can be obtained also when only one molecular transition is available. With our method, we obtain independent constraints from 12CO and 13CO, and we find they are in general good agreement using the standard 12C/13C isotopic ratio. The masses derived from our method are systematically lower compared with the values derived dynamically from the rotation curve if using an interstellar matter (ISM) CO abundance, implying that CO is depleted by a median factor ∼20 with respect to the ISM value, in line with other works that find that CO is depleted in protoplanetary disks.

Keywords: Protoplanetary disks, Planet formation
exoALMA. XVI. Predicting Signatures of Large-scale Turbulence in Protoplanetary Disks. Turbulent gas motions drive planet formation and protoplanetary disk evolution. However, empirical constraints on turbulence are scarce, halting our understanding of its nature. Resolving signatures of the large-scale perturbations driven by disk instabilities may reveal clues on the origin of turbulence in the outer regions of planet-forming disks. We aim to predict the observational signatures of such large-scale flows, as they would appear in high-resolution Atacama Large Millimeter/submillimeter Array observations of CO rotational lines, such as those conducted by the exoALMA Large Program. Post-processing 3D numerical simulations, we explored the observational signatures produced by three candidate (magneto)hydrodynamical instabilities to operate in the outer regions of protoplanetary disks: the vertical shear instability (VSI), the magnetorotational instability (MRI), and the gravitational instability (GI). We found that exoALMA-quality observations should capture signatures of the large-scale motions induced by these instabilities. Mainly, flows with ring, arc, and spiral morphologies are apparent in the residuals of synthetic velocity centroid maps. A qualitative comparison between our predictions and the perturbations recovered from exoALMA data suggests the presence of two laminar disks and a scarcity of ring- and arc-like VSI signatures within the sample. Spiral features produced by the MRI or the GI are still plausible in explaining observed disk perturbations. Supporting these scenarios requires further methodically comparing the predicted perturbations and the observed disks' complex dynamic structure.

Keywords: Hydrodynamical simulations, Radiative transfer simulations, Protoplanetary disks, Planet formation
exoALMA. XVII. Characterizing the Gas Dynamics around Dust Asymmetries. The key planet-formation processes in protoplanetary disks remain an active matter of research. One promising mechanism to radially and azimuthally trap millimeter-emitting dust grains, enabling them to concentrate and grow into planetesimals, is anticyclonic vortices. While dust observations have revealed crescent structures in several disks, observations of their kinematic signatures are still lacking. Studying the gas dynamics is, however, essential to confirm the presence of a vortex and understand its dust trapping properties. In this work, we make use of the high-resolution and sensitivity observations conducted by the exoALMA large program to search for such signatures in the 12CO and 13CO molecular line emission of four disks with azimuthal dust asymmetries: HD 135344B, HD 143006, HD 34282, and MWC 758. To assess the vortex features, we constructed an analytical vortex model and performed hydrodynamical simulations. For the latter, we assumed two scenarios: a vortex triggered at the edge of a dead zone and of a gap created by a massive embedded planet. These models reveal a complex kinematical morphology of the vortex. When compared to the data, we find that none of the sources show a distinctive vortex signature around the dust crescents in the kinematics. HD 135344B exhibits a prominent feature similar to the predictions from the simulations, thus making this the most promising target for sensitive follow-up studies at higher resolution and in particular with less abundant molecules at higher resolution and sensitivity to trace closer to the disk midplane.

Keywords: Submillimeter astronomy, Planetary-disk interactions, Protoplanetary disks, Planet formation
Observations of 1/f Noise at Mercury's Solar Wind Using MESSENGER Data. Low-frequency signals having a band-limited scale-invariant power, or "1/f" noise, have been detected in the interplanetary medium and inferred from coronal and photospheric observations. Their origin remains under debate, with the principal issue being whether the signal originates from local processes or has a solar origin, possibly emerging from a superposition of scale-invariant structures. Detection of such interplanetary signals at frequencies as low as a few times 10‑6 Hz at distances well within 1 au is important in developing an understanding of this phenomenon, but this is challenging due to a lack of the requisite long-duration data records. Here, we employ magnetic field data from the MESSENGER spacecraft, processed to remove Mercury's wake, to analyze spectra from a year of data. The 1/f signal is detected down to the lowest expected frequencies, consistent with the observed lognormal distribution of correlation times and the Machlup–Montroll–Shlesinger superposition principle. This supports the hypothesis that the observed 1/f signals have an origin in solar processes, possibly the dynamo, and disfavors local in situ generation, as described in W. H. Matthaeus &amp; M. L. Goldstein and W. H. Matthaeus et al.

Keywords: Solar wind, Interplanetary magnetic fields, Heliosphere
A Model-independent Radio Telescope Dark Matter Search in the L and S Bands. Ultralight bosonic dark matter in its most general form can be detected through its decay or annihilation to a quasimonochromatic radio line. Assuming only that this line is consistent with the most general properties of the expected phase space of our Milky Way halo, we have developed and carried out a novel model-independent search for dark matter in the L and S bands. More specifically, the search selects for a line that exhibits a Doppler shift with position according to the solar motion through a static halo and similarly varies in intensity with position with respect to the Galactic center. Over the combined L- and S-band range 1020–2700 MHz, radiative annihilation of dark matter is excluded above &lt;σv&gt; ≈ 10‑30 cm3 s‑1, and for decay above λ ≈ 10‑32 s‑1.

Keywords: Technosignatures, Radio astronomy, Dark matter, Doppler shift
The Discovery and Characterization of Earth-crossing Asteroid 2024 YR<SUB>4</SUB>. We describe observations and physical characteristics of Earth-crossing asteroid 2024 YR4, discovered on 2024 December 27 by the Asteroid Terrestrial-impact Last Alert System. The asteroid has semimajor axis a = 2.52 au, eccentricity e = 0.66, inclination i = 3 41, and a ∼0.003 au Earth minimum orbit intersection distance. We obtained g-, r-, i-, and Z-imaging with the Gemini South/Gemini Multi-Object Spectrograph on 2025 February 7 and Y and J imaging with the Keck/Multi-Object Spectrometer for Infrared Exploration on 2025 February 12. We measured a g − i spectral slope of 13% ± 3%/100 nm and color indices g − r = 0.70 ± 0.10, r − i = 0.25 ± 0.06, i − Z = −0.27 ± 0.10, and Y − J = 0.41 ± 0.10. 2024 YR4 has a spectrum that best matches R-type and Sa-type asteroids and a diameter of ∼30─65 m using our measured absolute magnitude of 23.9 ± 0.3 mag and assuming an albedo of 0.15─0.4. The lightcurve of 2024 YR4 shows ∼0.4 mag variations with a rotation period of ∼1170 s. We use photometry of 2024 YR4 from Gemini and other sources taken between 2024 December to 2025 February to determine the asteroid's spin vector and shape, finding that it has an oblate, ∼3:1 axial ratio and a pole direction of λ, β = ∼ 42∘, ∼−25∘. Finally, we compare the orbital elements of 2024 YR4 with the near-Earth object population model and find that its most likely sources are resonances between the inner and central Main Belt.

Keywords: Near-Earth objects, Asteroid rotation, Apollo group, Asteroid surfaces
Discovery of a Radio Megahalo in the Cluster PLCKG287.0+32.9 Using the uGMRT. We report the discovery of a radio megahalo in the merging cluster PLCKG287.0+32.9, based on upgraded Giant Metrewave Radio telescope (uGMRT) observations at frequencies 300–850 MHz. The sensitive radio observations provide a new window to study the complex physics occurring in this system. Apart from significant detections of the known diffuse radio emission in the cluster, we detect the central diffuse emission to a much larger extent of ∼3.2 Mpc, reaching the R500 of the cluster. The radial surface brightness profile shows a distinct flattening beyond ∼0.5R500, dividing the emission into inner and outer components. This outer envelope shows a steep spectral index (≲‑1.5) and emissivity ∼20 times lower than the inner component, confirming the megahalo characteristics. The radial profile of the spectral index also distinguishes the steep spectrum megahalo emission. Our observational results align with recent numerical simulations, showing megahalo emission oriented along the merger axis and the reacceleration of electrons driven by late-stage merger-induced turbulence. This is the first detection of a radio megahalo at a frequency higher than the LOFAR 144 MHz, opening the possibilities for more discoveries and spectral studies to understand their origin.

Keywords: Galaxy clusters, Extragalactic radio sources, Intracluster medium, Radio continuum emission