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Gas giant planets are formed by gas accretion onto planetary cores in protoplanetary disks. However, direct evidence of this process is still lacking, limiting our understanding of planetary formation processes. During mass accretion, planet-driven outflows may be launched, which could be observable by shock tracers such as sulfur monoxide (SO). We report the detection of SO gas in the protoplanetary disk around TW Hya in archival Atacama Large Millimeter/submillimeter Array observations. The SO J = 8 _7 − 7 _6 emission line is detected at a 6 σ significance and localized to the southeast region of the disk with an arc-like morphology. The line center is redshifted with respect to the systemic velocity by ∼5 km s ^−1 . The starting point of the SO emission is located at a planet-carved dust gap at 42 au. We attribute this to an outflow driven by an embedded protoplanet. Indeed, the observed morphology is well reproduced by a ballistic outflow model. The outflow velocity suggests that the outflow launching source has a mass of ∼4 M _⊕ and the mass-loss rate is 3 × 10 ^−8 –1 × 10 ^−6 M _Jup yr ^−1 . With the relation of mass-loss and mass-accretion rates established for protostars, we estimated the mass-accretion rate onto the protoplanet to be 3 × 10 ^−7 −1 × 10 ^−5 M _Jup yr ^−1 , which matches theoretical predictions for a ∼4 M _⊕ planet at this separation. The detection of planet-driven outflow provides us a unique opportunity to directly probe the earliest phase of gas giant planet formation.

Recent measurements of carbon isotope ratios in both protoplanetary disks and exoplanet atmospheres have suggested a possible transfer of significant carbon isotope fractionation from disks to planets. For a clearer understanding of the isotopic link between disks and planets, it is important to measure the carbon isotope ratios in various species. In this paper, we present a detection of the ^13 CN N = 2 − 1 hyperfine lines in the TW Hya disk with the Atacama Large Millimeter/submillimeter Array. This is the first spatially resolved detection of ^13 CN in disks, which enables us to measure the spatially resolved ^12 CN/ ^13 CN ratio for the first time. We conducted nonlocal thermal equilibrium modeling of the ^13 CN lines in conjunction with previously observed ^12 CN lines to derive the kinetic temperature, H _2 volume density, and column densities of ^12 CN and ^13 CN. The H _2 volume density is found to range between (4 − 10) × 10 ^7 cm ^−3 , suggesting that CN molecules mainly reside in the disk's upper layer. The ^12 CN/ ^13 CN ratio is measured to be ${70}_{-6}^{+9}$ at 30 < r < 80 au from the central star, which is similar to the ^12 C/ ^13 C ratio in the interstellar medium. However, this value differs from the previously reported values found for other carbon-bearing molecules (CO and HCN) in the TW Hya disk. This could be self-consistently explained by different emission layer heights for different molecules combined with preferential sequestration of ^12 C into the solid phase toward the disk midplane. This study reveals the complexity of the carbon isotope fractionation operating in disks.

Characterizing the physical properties of dust grains in a protoplanetary disk is critical to comprehending the planet formation process. Our study presents Atacama Large Millimeter/submillimeter Array (ALMA) high-resolution observations of the young protoplanetary disk around DG Tau at a 1.3 mm dust continuum. The observations, with a spatial resolution of ≈0.″04, or ≈5 au, revealed a geometrically thin and smooth disk without substantial substructures, suggesting that the disk retains the initial conditions of the planet formation. To further analyze the distributions of dust surface density, temperature, and grain size, we conducted a multiband analysis with several dust models, incorporating ALMA archival data of the 0.87 and 3.1 mm dust polarization. The results showed that the Toomre Q parameter is ≲2 at a 20 au radius, assuming a dust-to-gas mass ratio of 0.01. This implies that a higher dust-to-gas mass ratio is necessary to stabilize the disk. The grain sizes depend on the dust models, and for the DSHARP compact dust, they were found to be smaller than ∼400 μ m in the inner region ( r ≲ 20 au) while exceeding larger than 3 mm in the outer part. Radiative transfer calculations show that the dust scale height is lower than at least one-third of the gas scale height. These distributions of dust enrichment, grain sizes, and weak turbulence strength may have significant implications for the formation of planetesimals through mechanisms such as streaming instability. We also discuss the CO snowline effect and collisional fragmentation in dust coagulation for the origin of the dust size distribution.

Crescent-like asymmetric dust structures discovered in protoplanetary disks indicate dust aggregations. Thus, researching these structures helps us understand the planet formation process. Here we analyze ALMA data of the protoplanetary disk around the T-Tauri star SR 21, which has asymmetric structures that were detected in previous submillimeter observations. Imaged at ALMA Band 6 (1.3 mm) with a spatial resolution of about 0.″04, the disk is found to consist of two rings and three asymmetric structures, with two of the asymmetric structures being in the same ring. Compared to the Band 6 image, the Band 3 (2.7 mm) image also shows the three asymmetric structures, but with some clumps. The elongated asymmetric structures in the outer ring could be due to the interactions of a growing planet. Based on fitting the Band 3 and Band 6 dust continuum data, two branches of solutions for the maximum dust size in the disk are suggested: one is larger than 1 mm, and the other is smaller than 300 μ m. High-resolution continuum observations at longer wavelengths as well as polarization observations can help break the degeneracy. We also suggest that the prominent spiral previously identified in VLT/SPHERE observations south of the star at 0.″25 may be the scattered-light counterpart of the inner arc, and the structure is a dust-trapping vortex in nature. The discovered features in SR 21 make it a good target for studying the evolution of asymmetric structures and planet formation.

High-spatial-resolution observations of CO isotopologue line emission in protoplanetary disks at mid-inclinations (≈30°–75°) allow us to characterize the gas structure in detail, including radial and vertical substructures, emission surface heights and their dependencies on source characteristics, and disk temperature profiles. By combining observations of a suite of CO isotopologues, we can map the two-dimensional ( r , z ) disk structure from the disk upper atmosphere, as traced by CO, to near the midplane, as probed by less abundant isotopologues. Here, we present high-angular-resolution (≲0.″1 to ≈0.″2; ≈15–30 au) observations of CO, ^13 CO, and C ^18 O in either or both J = 2–1 and J = 3–2 lines in the transition disks around DM Tau, Sz 91, LkCa 15, and HD 34282. We derived line emission surfaces in CO for all disks and in ^13 CO for the DM Tau and LkCa 15 disks. With these observations, we do not resolve the vertical structure of C ^18 O in any disk, which is instead consistent with C ^18 O emission originating from the midplane. Both the J = 2–1 and J = 3–2 lines show similar heights. Using the derived emission surfaces, we computed radial and vertical gas temperature distributions for each disk, including empirical temperature models for the DM Tau and LkCa 15 disks. After combining our sample with literature sources, we find that ^13 CO line emitting heights are also tentatively linked with source characteristics, e.g., stellar host mass, gas temperature, disk size, and show steeper trends than seen in CO emission surfaces.

The mass distribution of dense cores is a potential key to understanding the process of star formation. Applying dendrogram analysis to the CARMA-NRO Orion C ^18 O ( J = 1–0) data, we identify 2342 dense cores, about 22% of which have virial ratios smaller than 2 and can be classified as gravitationally bound cores. The derived core mass function (CMF) for bound starless cores that are not associate with protostars has a slope similar to Salpeter’s initial mass function (IMF) for the mass range above 1 M _⊙ , with a peak at ∼0.1 M _⊙ . We divide the cloud into four parts based on decl., OMC-1/2/3, OMC-4/5, L1641N/V380 Ori, and L1641C, and derive the CMFs in these regions. We find that starless cores with masses greater than 10 M _⊙ exist only in OMC-1/2/3, whereas the CMFs in OMC-4/5, L1641N, and L1641C are truncated at around 5–10 M _⊙ . From the number ratio of bound starless cores and Class II objects in each subregion, the lifetime of bound starless cores is estimated to be 5–30 freefall times, consistent with previous studies for other regions. In addition, we discuss core growth by mass accretion from the surrounding cloud material to explain the coincidence of peak masses between IMFs and CMFs. The mass accretion rate required for doubling the core mass within a core lifetime is larger than that of Bondi–Hoyle accretion by a factor of order 2. This implies that more dynamical accretion processes are required to grow cores.

Characterizing the physical properties of dust grains in a protoplanetary disk is critical to comprehending the planet formation process. Our study presents Atacama Large Millimeter/submillimeter Array (ALMA) high-resolution observations of the young protoplanetary disk around DG Tau at a 1.3 mm dust continuum. The observations, with a spatial resolution of ≈0.″04, or ≈5 au, revealed a geometrically thin and smooth disk without substantial substructures, suggesting that the disk retains the initial conditions of the planet formation. To further analyze the distributions of dust surface density, temperature, and grain size, we conducted a multiband analysis with several dust models, incorporating ALMA archival data of the 0.87 and 3.1 mm dust polarization. The results showed that the Toomre Q parameter is ≲2 at a 20 au radius, assuming a dust-to-gas mass ratio of 0.01. This implies that a higher dust-to-gas mass ratio is necessary to stabilize the disk. The grain sizes depend on the dust models, and for the DSHARP compact dust, they were found to be smaller than ∼400 μ m in the inner region (r ≲ 20 au) while exceeding larger than 3 mm in the outer part. Radiative transfer calculations show that the dust scale height is lower than at least one-third of the gas scale height. These distributions of dust enrichment, grain sizes, and weak turbulence strength may have significant implications for the formation of planetesimals through mechanisms such as streaming instability. We also discuss the CO snowline effect and collisional fragmentation in dust coagulation for the origin of the dust size distribution. [ABSTRACT FROM AUTHOR]

Crescent-like asymmetric dust structures discovered in protoplanetary disks indicate dust aggregations. Thus, researching these structures helps us understand the planet formation process. Here we analyze ALMA data of the protoplanetary disk around the T-Tauri star SR 21, which has asymmetric structures that were detected in previous submillimeter observations. Imaged at ALMA Band 6 (1.3 mm) with a spatial resolution of about 0.″04, the disk is found to consist of two rings and three asymmetric structures, with two of the asymmetric structures being in the same ring. Compared to the Band 6 image, the Band 3 (2.7 mm) image also shows the three asymmetric structures, but with some clumps. The elongated asymmetric structures in the outer ring could be due to the interactions of a growing planet. Based on fitting the Band 3 and Band 6 dust continuum data, two branches of solutions for the maximum dust size in the disk are suggested: one is larger than 1 mm, and the other is smaller than 300 μ m. High-resolution continuum observations at longer wavelengths as well as polarization observations can help break the degeneracy. We also suggest that the prominent spiral previously identified in VLT/SPHERE observations south of the star at 0.″25 may be the scattered-light counterpart of the inner arc, and the structure is a dust-trapping vortex in nature. The discovered features in SR 21 make it a good target for studying the evolution of asymmetric structures and planet formation. [ABSTRACT FROM AUTHOR]

Newly discovered nanomaterials are expected to be applied as elements in new functional electronics. Since the discovery of fullerene, scanning tunneling microscopy under ultrahigh vacuum and a cryogenic temperature has been a popular method of extracting the properties of single molecules. However, some nanoelements exhibit a function based on a single-molecule property even though they are embedded in a cluster. Here, we present our experimental demonstration of a single-fullerene motion resistive switching device for functional fullerene electronics, which can be realized in crystal nanowires (NWs). We fabricated a two-terminal device using fullerene self-assembled C60 NWs, which can be synthesized by dispersing fullerenes in a solution, keeping them in a supersaturated state, and maintaining a liquid–liquid interface. We found that the C60 NW device can be operated at room temperature and can reproducibly perform several hundred repetitive switch operations. The reproducibility of the device fabrication is high, and we expect the appearance of integrated devices based on the results of our experiments. In this progress review of our C60 switching device, we describe details of the device fabrication and electric operation that take advantage of the various properties inherent in fullerenes for reproducible future minimal-scale switching systems [Umeta, H. et al., ACS Appl. Nano Mater. 4, 820 (2021)]. [ABSTRACT FROM AUTHOR]

Compact protoplanetary disks with a radius of ≲50 au are common around young low-mass stars. We report high-resolution ALMA dust continuum observations toward a compact disk around CW Tau at Bands 4 (λ = 2.2 mm), 6 (1.3 mm), 7 (0.89 mm), and 8 (0.75 mm). The spectral energy distribution shows the spectral slope of 2.0 ± 0.24 between 0.75 and 1.3 mm, while it is 3.7 ± 0.29 between 2.17 and 3.56 mm. The steep slope between 2.17 and 3.56 mm is consistent with that of optically thin emission from small grains (≲350 ÎĽ m). We perform parametric fitting of the ALMA data to characterize the dust disk. Interestingly, if the dust-to-gas mass ratio is 0.01, the Toomre Q parameter reaches ∼1â€"3, suggesting that the CW Tau disk might be marginally gravitationally unstable. The total dust mass is estimated as ∼250 M ⊕ for the maximum dust size of 140 ÎĽ m that is inferred from the previous Band 7 polarimetric observation and at least 80 M ⊕ even for larger grain sizes. This result shows that the CW Tau disk is quite massive in spite of its smallness. Furthermore, we clearly identify a gap structure located at ∼20 au, which might be induced by a giant planet. In spite of these interesting characteristics, the CW Tau disk has normal disk luminosity, size, and spectral index at ALMA Band 6, which could be a clue to the mass budget problem in Class II disks. [ABSTRACT FROM AUTHOR]

The oxygen isotope fractionation scenario, which has been developed to explain the oxygen isotope anomaly in solar system materials, predicts that CO gas is depleted in 18O in protoplanetary disks, where segregation between solids and gas inside disks has already occurred. Based on Atacama Large Millimeter/submillimeter Array observations, we report the first detection of HC18O+(4–3) in a Class II protoplanetary disk (TW Hya). This detection allows us to explore the oxygen isotope fractionation of CO in the disk from optically thin HCO+ isotopologues as a proxy of optically thicker CO isotopologues. Using the H13CO+(4–3) data previously obtained with the SMA, we find that the H13CO+/HC18O+ ratio in the central ≲100 au regions of the disk is 10.3 ± 3.2. We construct a chemical model of the TW Hya disk with carbon and oxygen isotope fractionation chemistry, and estimate the conversion factor from H13CO+/HC18O+ to 13CO/C18O. With the conversion factor (=0.8), the 13CO/C18O ratio is estimated to be 8.3 ± 2.6, which is consistent with the elemental abundance ratio in the local interstellar medium (8.1 ± 0.8) within the error margin. Therefore, there is no clear evidence of 18O depletion in CO gas in the central ≲100 au regions of the disk, although we could not draw a robust conclusion due to uncertainties. In conclusion, optically thin lines of HCO+ isotopologues are useful tracers of CO isotopic ratios, which are not very constrained directly from optically thick lines of CO isotopologues. Future higher sensitivity observations of H13CO+ and HC18O+ would allow us to better constrain the oxygen fractionation in the disk. [ABSTRACT FROM AUTHOR]

We present molecular line observations of 13CO and C18O J = 3 − 2, CN N = 3 − 2, and CS J = 7 − 6 lines in the protoplanetary disk around TW Hya at a high spatial resolution of ∼9 au (angular resolution of 0.″15), using the Atacama Large Millimeter/Submillimeter Array. A possible gas gap is found in the deprojected radial intensity profile of the integrated C18O line around a disk radius of ∼58 au, slightly beyond the location of the au-scale dust clump at ∼52 au, which resembles predictions from hydrodynamic simulations of planet–disk interaction. In addition, we construct models for the physical and chemical structure of the TW Hya disk, taking account of the dust surface density profile obtained from high spatial resolution dust continuum observations. As a result, the observed flat radial profile of the CN line intensities is reproduced due to a high dust-to-gas surface density ratio inside ∼20 au. Meanwhile, the CO isotopologue line intensities trace high temperature gas and increase rapidly inside a disk radius of ∼30 au. A model with either CO gas depletion or depletion of gas-phase oxygen elemental abundance is required to reproduce the relatively weak CO isotopologue line intensities observed in the outer disk, consistent with previous atomic and molecular line observations toward the TW Hya disk. Further observations of line emission of carbon-bearing species, such as atomic carbon and HCN, with high spatial resolution would help to better constrain the distribution of elemental carbon abundance in the disk gas. [ABSTRACT FROM AUTHOR]

We report an analysis of the dust disk around DM Tau, newly observed with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3 mm. The ALMA observations with high sensitivity (8.4 μJy beam–1) and high angular resolution (35 mas, 5.1 au) detect two asymmetries on the ring at r ∼ 20 au. They could be two vortices in early evolution, the destruction of a large-scale vortex, or double continuum emission peaks with different dust sizes. We also found millimeter emissions with ∼50 μJy (a lower-limit dust mass of 0.3 MMoon) inside the 3 au ring. To characterize these emissions, we modeled the spectral energy distribution (SED) of DM Tau using a Monte Carlo radiative transfer code. We found that an additional ring at r = 1 au could explain both the DM Tau SED and the central point source. The disk midplane temperature at the 1 au ring calculated in our modeling is less than the typical water sublimation temperature of 150 K, prompting the possibility of forming small icy planets there. [ABSTRACT FROM AUTHOR]

Characteristics of thin-film transistors (TFTs) with amorphous In2O3 (InO1.2) and carbon-doped In2O3 (InO1.16C0.04) channels by post-metallization annealing (PMA) process were investigated. The InO1.2 TFT changed from metallic to switching behavior after PMA at 200 °C. In contrast, the InO1.16C0.04 TFT exhibited superior properties such as a threshold voltage (Vth) of 3.2 V and a high mobility of 20.4 cm2 V−1 s−1 at PMA 150 °C because of the reduction of excess oxygen vacancies. A large negative Vth shift was observed for the InO1.2 TFT for 10 800 s in N2 under zero bias voltage while there was no Vth change for the InO1.16C0.04 TFT. [ABSTRACT FROM AUTHOR]

With an emphasis on improving the fidelity even in super-resolution regimes, new imaging techniques have been intensively developed over the last several years, which may provide substantial improvements to the interferometric observation of protoplanetary disks. In this study, sparse modeling (SpM) is applied for the first time to observational data sets taken by the Atacama Large Millimeter/submillimeter Array (ALMA). The two data sets used in this study were taken independently using different array configurations at Band 7 (330 GHz), targeting the protoplanetary disk around HD 142527: one in the shorter-baseline array configuration (∼430 m), and the other in the longer-baseline array configuration (∼1570 m). The image resolutions reconstructed from the two data sets are different by a factor of ∼3. We confirm that the previously known disk structures appear on the images produced by both SpM and CLEAN at the standard beam size. The image reconstructed from the shorter-baseline data using the SpM matches that obtained with the longer-baseline data using the CLEAN, achieving a super-resolution image from which a structure finer than the beam size can be reproduced. Our results demonstrate that ongoing intensive development in the SpM imaging technique is beneficial to imaging with ALMA. [ABSTRACT FROM AUTHOR]

Dust continuum observation is one of the best methods to constrain the properties of protoplanetary disks. Recent theoretical studies have suggested that dust scattering at the millimeter wavelength potentially reduces the observed intensity, which results in an underestimate in the dust mass. We investigate whether dust scattering indeed reduces the observed continuum intensity by comparing the ALMA archival data of the TW Hya disk at Bands 3, 4, 6, 7, and 9 to models obtained by radiative transfer simulations. We find that the model with scattering by 300 μm-sized grains well reproduces the observed spectral energy distribution of the central part of the TW Hya disk while the model without scattering is also consistent within the errors of the absolute fluxes. To explain the intensity at Band 3, the dust surface density needs to be ∼10 g cm−2 at 10 au in the model with scattering, which is 26 times more massive than previously predicted. The model without scattering needs a 2.3 times higher dust mass than the model with scattering because it needs a lower temperature. At Band 7, scattering reduces the intensity by ∼35%, which makes the disk look optically thin even though it is optically thick. Our study suggests the TW Hya disk is still capable of forming cores of giant planets at locations analogous to where the current solar system planets exist. [ABSTRACT FROM AUTHOR]