arXiv subjects

Daniel Harsono

Publications and source records attributed to Daniel Harsono.

At least 19 recordsLinked to original sources

arXiv2026

ALOHA IRDCs Molecular Line Follow-up: I. Gas properties and kinematics

Infrared Dark Clouds are ideal sites for investigating the initial conditions of massive star and cluster formation. The A Lei Of the Habitat and Assembly of Infrared Dark Clouds (ALOHA IRDCs), a James Clerk Maxwell Telescope (JCMT) Large Program, has mapped nearby IRDCs with SCUBA-2. Complementary molecular line observations are needed to characterise the physical, kinematic, and chemical properties of the dense gas. We aim to determine the thermal, kinematic, and chemical properties of clumps identified in the ALOHA IRDCs, and to assess their evolutionary status and level of star-forming activity. We performed single-pointing K-band and W-band observations towards 56 ALOHA IRDCs clumps using the Effelsberg 100-m and Yebes 40-m telescopes, respectively. We derived NH3 kinetic temperatures using the hyperfine group ratio (HFGR) method and identified infall and shock signatures from HCO+, H13CO+, SiO, and HNCO profiles. Water masers and NH2D emission were used as complementary tracers of chemical evolution and star formation. The clumps exhibit kinetic temperatures of 15-29 K. We detect NH2D emission towards 18 sources, with NH2D centroid velocities consistent with NH3, indicating both species trace the same dense gas component. More than half of the clumps display blue-asymmetric HCO+ profiles, identifying them as infall candidates. Water masers are detected in 22 sources, with prominent velocity ranges and variability. Broad SiO emission (>~20 km/s) indicates strong shocks, while narrower extents (<~6km/s) likely trace large-scale interactions or low-velocity shocks. The widespread infall signatures, shock tracers, masers, and NH2D emission suggest that relatively quiescent, chemically young material can coexist with dynamically active gas affected by early protostellar feedback, providing insight into the coupled physical and chemical evolution of massive IRDC clumps.

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arXiv2026

A Chemical Inventory of the Disk around the Class 0 Protostar L1527 IRS with ALMA

Planet formation starts in disks that are still embedded within their natal envelopes. Here, we compile an extensive inventory of the chemical composition of the disk and envelope ($<$ 3500 au) around the Class 0 protostar L1527 IRS. Using all publicly available ALMA (Atacama Large Millimeter/submillimeter Array) data, we report the detection of 40 molecules, including isotopologues. Of these, 23 are different molecular species and 29 are reported here for the first time toward L1527 in ALMA observations. CH$_3$OH is the only complex organic molecule detected, while the hydrocarbon CH$_3$CCH is the largest molecule detected. Overall, only a few programs are sensitive enough to detect emission unambiguously originating from the disk based on the kinematics. Nitrogen-bearing molecules are predominantly detected on more extended scales, while hydrocarbons show a distinct tail roughly along the southeastern outflow cavity wall, probably due to a stronger UV field in the eastern outflow lobe. The L1527 IRS protostellar system is not rich in sulfur-bearing molecules, with only strong emission observed for CS and SO. Overall, the envelope appears dominated by a carbon-rich chemistry, which seems to transition into an oxygen-rich chemistry in the disk. We calculate column densities of all detected species, providing a starting point to quantify the chemical diversity among young disks and the chemical evolution of the planet-forming material.

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arXiv2026

JWST Edge-on Disk Ice (JEDIce): Vibrationally hot, rotationally cold H$_2$ in the outer disk of Oph 163131 non-thermally excited by UV and cosmic rays

Constraining ionization and excitation processes in protoplanetary disks is essential for understanding the chemical structure and evolution of disk material, shaping planet formation pathways. We present JWST/NIRSpec IFU observations of the edge-on disk Oph 163131, which reveal a unusual ro-vibrational H$_2$ spectrum dominated by the 1--0 O(2) line (2.627 $\mu$m), with suppressed higher-$J$ emission despite excitation to $v=2$ and $3$. This vibrationally hot, rotationally cold H$_2$ emission is spatially extended, broadly following the molecular disk traced by CO($J{=}2$--1), with emission increasing above and below a thin midplane dark lane and extending radially beyond $\sim$200 au, where near-IR scattered-light emission is no longer dominant. We interpret the observed H$_2$ emission as arising from non-thermal excitation in cold, dense outer-disk gas, where collisions depopulate higher-$J$ rotational levels within each vibrational manifold prior to emission, producing the characteristic ``$v$-hot, $J$-cold" spectrum. We consider both ultraviolet irradiation and cosmic-ray excitation as contributors to the H$_2$ emission and find that their combined action, together with collisional de-excitation of high-$J$ level populations, broadly reproduces the observed line ratios and morphology. Within this framework, we infer a rather high effective cosmic-ray ionization rate of $\sim(1$-$10)\times10^{-15}$ s$^{-1}$ in the presence of a moderate UV field ($\chi_{UV}=100-1000$, in Draine units). These results for disks, together with the recent findings by Bialy et al. 2025 for the lower-density starless core B68, highlight the potential of ro-vibrational H$_2$ emission as a novel probe of cosmic-ray ionization.

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arXiv2026

JOYS: Launching and destruction of dust in protostellar jets. The case of BHR71-IRS1 with JWST/MIRI

Protostellar winds can theoretically lift solids from the planet-forming disks, but direct evidence for launched dust has been scarce so far. Numerous atomic lines that are unique to mid-infrared (IR) wavelengths reveal refractories eroded from dust grains and provide information on wind properties in the earliest stages of the star formation process. We present JWST/MIRI-MRS spectral imaging of the inner 2000 au of the BHR71-IRS1 blueshifted side of the outflow. Atomic line intensities are compared to shock models to constrain the physical conditions and elemental abundances of the outflowing gas. Dust continuum maps are constructed from PSF-subtracted cubes, and the dust spectral energy distribution is analyzed. The ionized central jet of BHR71-IRS1 is spatially resolved and imaged for the first time, revealing a unique inventory of refractory, volatile, and noble-gas fine-structure lines (Fe, Ni, Co, Cl, S, Ne, Ar). The emission is concentrated along four bright knots that wiggle along the jet axis. PSF-subtracted continuum maps reveal extended mid-IR continuum emission co-spatial with the jet bullets and within the H$_2$-traced outflow cone. Spectral energy distributions along the jet are fit together with the extinction, revealing a warm (200-400 K) and a cold (70-90 K) dust component. Shock modeling constrained by the mid-IR lines indicates a decline in shock velocity from 70 to 35 km s$^{-1}$ and pre-shock density from $>$10$^5$ to $ 4\times 10^4$ cm$^{-3}$ with distance from the protostar. Gas-phase Fe and Ni are measurably depleted relative to Solar abundances, consistent with a substantial fraction of refractories remaining locked in grains in spite of the shocks. These JWST observations provide direct evidence that dust is launched in a Class 0 jet and at least partly survives shock processing.

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arXiv2026

JWST Edge-on Disk Ice (JEDIce): Program overview and ice survey results

The icy material within protoplanetary disks plays a central role in planet formation, yet remains poorly characterized by observations. We present 1.6-28$\mu$m spectra of five disks obtained as part of the JWST Edge-on Disk Ice (JEDIce) program, representing the largest survey of disk ices to date. The major ice species H$_2$O, CO$_2$, and CO are detected towards all disks, and exhibit a wide range of absolute optical depths and optical depth ratios across the sample. This is suggestive of a range of ice abundances and compositions, but quantitative constraints will require radiative transfer modeling. All disks exhibit ice features across the entire spatial region where the IR continuum is detected; vertically elevated ice grains therefore seem to be ubiquitous in disks. The CO ice is consistently dominated by apolar CO:CO$_2$ mixtures, implying that the disk ice compositions are neither completely reset nor pristinely inherited from the protostellar stage. The presence of these mixtures also suggests that entrapment may be important in shaping the spatial distribution of CO within the disks. Small molecules commonly seen in protostellar ices (CH$_4$, CH$_3$OH, NH$_3$) are generally not detected in our sample, though tracers of ammonium salts (OCN$^-$ and the 6.85 $\mu$m band) are common, potentially reflecting an evolution towards comet-like ice compositions. The spectra also contain a wealth of information about the micron-sized dust, atomic and molecular gas, and PAH content, which together with the ice constraints will provide a comprehensive picture of the chemical, physical, and dynamical state of these systems.

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arXiv2026

Probing Dust in the MWC 480 Disk from Millimeter to Centimeter Wavelengths

We present deep, high-resolution ($\sim$100 mas) Karl G. Jansky Very Large Array (VLA) Ka-band (9.1 mm) observations of the disk around MWC 480, and infer dust properties through a combined analysis with archival Atacama Large Millimeter/submillimeter Array (ALMA) data at 0.87, 1.17, 1.33, and 3.0 mm. The prominent dust ring at 95 au (B95) is detected at 9.1 mm for the first time, while the faint outer ring at 160 au is not revealed. Through non-parametric visibility modeling, we identified two new annular features: a plateau within 20-50 au across all wavelengths, and a shoulder exterior to the B95 ring at 0.87, 1.17 and 1.33 mm, consistent with signatures of planet-disk interaction. We find that the width of the B95 ring remains constant across wavelengths, suggesting that fragmentation dominates over radial diffusion or that unresolved substructure is present within the ring. Resolved spectral modeling yields two families of dust solutions that reproduce the observations equally well: compact grains or highly porous (90\%) grains, with carbonaceous components dominated by refractory organics or amorphous carbon, respectively. The inferred maximum grain sizes peak at the locations of the two rings and reach centimeter within the B95 ring. The total dust masses are $860^{+95}_{-78}\rm~M_\oplus$/$1500^{+440}_{-330}\rm~M_\oplus$ (large/small-grain solution in inner disk) and $230^{+14}_{-13}\rm~M_\oplus$ for the two dust mixtures. The B95 ring alone contains $100^{+5}_{-5}\rm~M_\oplus$ and $43^{+2}_{-2}\rm~M_\oplus$, respectively, sufficient to assemble the cores of giant planets. Finally, we highlight the power of broadband, multi-wavelength observations in placing better constraints on dust composition and porosity in protoplanetary disks.

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arXiv2025

The Flying Saucer edge-on disc's Near Infrared silhouette revealed by the JWST JEDIce program

Edge-on discs offer a unique opportunity to probe radial and vertical dust and gas distributions in the protoplanetary phase. This study aims to investigate the distribution of micron-sized dust particles in the Flying Saucer (BKLT J162813-243139) in Rho Ophiuchi, leveraging the unique observational conditions of a bright infrared background that enables the edge-on disc to be seen in both silhouette and scattered light at certain, specific wavelengths. As part of the JWST Edge-on Disc Ice program ('JEDIce'), we use NIRSpec IFU observations of the Flying Saucer, serendipitously observed against a PAH-emitting background, to constrain the dust distribution and grain sizes through radiative transfer modelling. Observation of the Flying Saucer in silhouette at 3.29 microns reveals that the midplane radial extent of small dust grains is ~235 au, larger than the large-grain disc extent previously determined to be 190 au from millimetre data. The scattered light observed in emission probes micron sized icy grains at large vertical distances above the midplane. The vertical extent of the disc silhouette is similar at visible, near-IR, and mid-IR wavelengths, corroborating the conclusion that dust settling is inefficient for grains as large as tens of microns, vertically and radially.

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arXiv2024

The First JWST View of a 30-Myr-old Protoplanetary Disk Reveals a Late-stage Carbon-rich Phase

We present a JWST MIRI/MRS spectrum of the inner disk of WISE J044634.16$-$262756.1B (hereafter J0446B), an old ($\sim$34 Myr) M4.5 star but with hints of ongoing accretion. The spectrum is molecule-rich and dominated by hydrocarbons. We detect 14 molecular species (H$_2$, CH$_3$, CH$_4$, C$_2$H$_2$, $^{13}$CCH$_2$, C$_2$H$_4$, C$_2$H$_6$, C$_3$H$_4$, C$_4$H$_2$, C$_6$H$_6$, HCN, HC$_3$N, CO$_2$ and $^{13}$CO$_2$) and 2 atomic lines ([Ne II] and [Ar II]), all observed for the first time in a disk at this age. The detection of spatially unresolved H$_2$ and Ne gas strongly supports that J0446B hosts a long-lived primordial disk, rather than a debris disk. The marginal H$_2$O detection and the high C$_2$H$_2$/CO$_2$ column density ratio indicate that the inner disk of J0446B has a very carbon-rich chemistry, with a gas-phase C/O ratio $\gtrsim$2, consistent with what have been found in most primordial disks around similarly low-mass stars. In the absence of significant outer disk dust substructures, inner disks are expected to first become water-rich due to the rapid inward drift of icy pebbles, and evolve into carbon-rich as outer disk gas flows inward on longer timescales. The faint millimeter emission in such low-mass star disks implies that they may have depleted their outer icy pebble reservoir early and already passed the water-rich phase. Models with pebble drift and volatile transport suggest that maintaining a carbon-rich chemistry for tens of Myr likely requires a slowly evolving disk with $\alpha-$viscosity $\lesssim10^{-4}$. This study represents the first detailed characterization of disk gas at $\sim$30 Myr, strongly motivating further studies into the final stages of disk evolution.

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arXiv2024

JWST ice band profiles reveal mixed ice compositions in the HH 48 NE disk

Planet formation is strongly influenced by the composition and distribution of volatiles within protoplanetary disks. With JWST, it is now possible to obtain direct observational constraints on disk ices, as recently demonstrated by the detection of ice absorption features towards the edge-on HH 48 NE disk as part of the Ice Age Early Release Science program. Here, we introduce a new radiative transfer modeling framework designed to retrieve the composition and mixing status of disk ices using their band profiles, and apply it to interpret the H2O, CO2, and CO ice bands observed towards the HH 48 NE disk. We show that the ices are largely present as mixtures, with strong evidence for CO trapping in both H2O and CO2 ice. The HH 48 NE disk ice composition (pure vs. polar vs. apolar fractions) is markedly different from earlier protostellar stages, implying thermal and/or chemical reprocessing during the formation or evolution of the disk. We infer low ice-phase C/O ratios around 0.1 throughout the disk, and also demonstrate that the mixing and entrapment of disk ices can dramatically affect the radial dependence of the C/O ratio. It is therefore imperative that realistic disk ice compositions are considered when comparing planetary compositions with potential formation scenarios, which will fortunately be possible for an increasing number of disks with JWST.

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arXiv2024

JCMT 850 $\micron$ continuum observations of density structures in the G35 molecular complex

Filaments are believed to play a key role in high-mass star formation. We present a systematic study of the filaments and their hosting clumps in the G35 molecular complex using JCMT SCUBA-2 850 $\micron$ continuum data. We identified five clouds in the complex and 91 filaments within them, some of which form 10 hub-filament systems (HFSs), each with at least 3 hub-composing filaments. We also compiled a catalogue of 350 dense clumps, 183 of which are associated with the filaments. We investigated the physical properties of the filaments and clumps, such as mass, density, and size, and their relation to star formation. We find that the global mass-length trend of the filaments is consistent with a turbulent origin, while the hub-composing filaments of high line masses ($m_{\rm l}\,>$\,230\,$\mathrm{M_{\odot}~pc^{-1}}$) in HFSs deviate from this relation, possibly due to feedback from massive star formation. We also find that the most massive and densest clumps (R\,$>$\,0.2\,pc, M\,$>35\,\mathrm{M_{\odot}}$, $\mathrm{\Sigma}>\,0.05\,\mathrm{g~cm^{-2}}$) are located in the filaments and in the hubs of HFS with the latter bearing a higher probability of occurrence of high-mass star-forming signatures, highlighting the preferential sites of HFSs for high-mass star formation. We do not find significant variation in the clump mass surface density across different evolutionary environments of the clouds, which may reflect the balance between mass accretion and stellar feedback.

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arXiv2024

The Asymmetric Bipolar Fe II Jet and H2 Outflow of TMC1A Resolved with JWST's NIRSpec IFU

(abridged) Protostellar outflows exhibit large variations in their structure depending on the observed gas emission. This study analyzes the atomic jet and molecular outflow in the Class I protostar, TMC1A to characterize morphology and identify previously undetected spatial features with JWST's NIRSpec IFU. In addition to identifying a large number of Fe II and H2 lines, we have detected the bipolar Fe jet by revealing, for the first time, the presence of a red-shifted atomic jet. Similarly, the red-shifted component of the H2 slower wide-angle outflow is observed. Both Fe II and H2 red-shifted emission exhibit significantly lower flux densities compared to their blue-shifted counterparts. Additionally, we report the detection of a collimated high-velocity (100 km s-1), blue-shifted H2 outflow, suggesting the presence of a molecular jet in addition to the well-known wider angle low-velocity structure. The Fe II and H2 jets show multiple intensity peaks along the jet axis, which may be associated with ongoing or recent outburst events. In addition to the variation in their intensities, the H2 wide-angle outflow exhibits a "ring"-like structure. The blue-shifted H2 outflow also shows a left-right brightness asymmetry likely due to interactions with the surrounding ambient medium and molecular outflows. Using the Fe II line ratios, the extinction along the atomic jet is estimated to be between Av = 10-30 on the blue-shifted side, with a trend of decreasing extinction with distance from the protostar. A similar Av is found for the red-shifted side, supporting the argument for an intrinsic red-blue outflow lobe asymmetry rather than environmental effects such as extinction. This intrinsic difference revealed by the unprecedented sensitivity of JWST, suggests that younger outflows already exhibit the red-blue side asymmetry more commonly observed towards jets associated with Class II disks.

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arXiv2024

Small and Large Dust Cavities in Disks around mid-M Stars in Taurus

High-angular resolution imaging by ALMA has revealed the near-universality and diversity of substructures in protoplanetary disks. However, disks around M-type pre-main-sequence stars are still poorly sampled, despite the prevalence of M-dwarfs in the galaxy. Here we present high-resolution (~50 mas, 8 au) ALMA Band 6 observations of six disks around mid-M stars in Taurus. We detect dust continuum emission in all six disks, 12CO in five disks, and 13CO line in two disks. The size ratios between gas and dust disks range from 1.6 to 5.1. The ratio of about 5 for 2M0436 and 2M0450 indicates efficient dust radial drift. Four disks show rings and cavities and two disks are smooth. The cavity sizes occupy a wide range: 60 au for 2M0412, and ~10 au for 2M0434, 2M0436 and 2M0508. Detailed visibility modeling indicates that small cavities of 1.7 and 5.7 au may hide in the two smooth disks 2M0450 and CIDA 12. We perform radiative transfer fitting of the infrared SEDs to constrain the cavity sizes, finding that micron-sized dust grains may have smaller cavities than millimeter grains. Planet-disk interactions are the preferred explanation to produce the large 60 au cavity, while other physics could be responsible for the three ~10 au cavities under current observations and theories. Currently, disks around mid-to-late M stars in Taurus show a higher detection frequency of cavities than earlier type stars, although a more complete sample is needed to evaluate any dependence of substructure on stellar mass.

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arXiv2023

Dual-Band Observations of the Asymmetric Ring around CIDA 9A: Dead or Alive?

While the most exciting explanation of the observed dust asymmetries in protoplanetary disks is the presence of protoplanets, other mechanisms can also form the dust features. This paper presents dual-wavelength Atacama Large Millimeter/submillimeter Array (ALMA) observations of a large asymmetric dusty ring around the M-type star CIDA 9A. We detect a dust asymmetry in both 1.3 mm and 3.1 mm data. To characterize the asymmetric structure, a parametric model is used to fit the observed visibilities. We report a tentative azimuthal shift of the dust emission peaks between the observations at the two wavelengths. This shift is consistent with a dust trap caused by a vortex, which may be formed by an embedded protoplanet or other hydrodynamical instabilities, such as a dead zone. Deep high-spatial observations of dust and molecular gas are needed to constrain the mechanisms that formed the observed millimeter cavity and dust asymmetry in the protoplanetary disk around CIDA 9A.

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arXiv2023

A high HDO/H$_{2}$O ratio in the Class I protostar L1551 IRS5

Water is a very abundant molecule in star-forming regions. Its deuterium fractionation is an important tool for understanding its formation and evolution during the star and planet formation processes. While the HDO/H$_2$O ratio has been determined toward several Class 0 protostars and comets, the number of studies toward Class I protostars is limited. We aim to study the water deuteration toward the Class I binary protostar L1551 IRS5 and to investigate the effect of evolutionary stage and environment on variations in the water D/H ratio. Observations were made using the NOEMA interferometer. The HDO 3$_{1,2}$-2$_{2,1}$ transition at 225.9 GHz and the H$_2^{18}$O 3$_{1,3}$-2$_{2,0}$ transition at 203.4 GHz were covered with a spatial resolution of 0.5'' $\times$ 0.8'', while the HDO 4$_{2,2}$-4$_{2,3}$ transition at 143.7 GHz was observed with a resolution of 2.0'' $\times$ 2.5''. We used both LTE and non-LTE models. The three transitions are detected. The line profiles display two peaks, one at $\sim$6 km s$^{-1}$ and one at $\sim$9 km s$^{-1}$. We derive an HDO/H$_2$O ratio of (2.1 $\pm$ 0.8) $\times$ 10$^{-3}$ for the redshifted component and a lower limit of $>$ 0.3 $\times$ 10$^{-3}$ for the blueshifted component due to the blending with the redshifted CH$_3$OCH$_3$ emission. The HDO/H$_2$O in L1551 IRS5 is similar to the ratios in isolated Class 0 sources and to the Class I V883 Ori, while it is significantly higher than in the clustered Class 0 sources and the comets. This suggests that the chemistry of protostars in low source densities clouds share more similarities with the isolated sources than the protostars of very dense clusters. If Class 0 protostars with few sources around and isolated Class 0 objects are comparable in the HDO/H$_2$O ratio, it would mean that there is little water reprocessing from the Class 0 to Class I protostellar stage.

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arXiv2023

Episodic infall towards a compact disk in B335?

Previous observations of B335 have presented evidence of ongoing infall in various molecular lines, e.g., HCO$^+$, HCN, CO. There have been no confirmed observations of a rotationally supported disk on scales greater than ~12~au. The presence of an outflow in B335 suggests that also a disk should be present or in formation. To constrain the earliest stages of protostellar evolution and disk formation, we aim to map the region where gas falls inwards and observationally constrain its kinematics. Furthermore, we aim to put strong limits on the size and orientation of any disk-like structure in B335. We use high angular resolution $^{13}$CO data from ALMA, and combine it with shorter-baseline archival data to produce a high-fidelity image of the infall in B335. We also revisit the imaging of high-angular resolution Band 6 continuum data to study the dust distribution in the immediate vicinity of B335. Continuum emission shows an elliptical structure (10 by 7 au) with a position angle 5 degrees east of north, consistent with the expectation for a forming disk in B335. A map of the infall velocity (as estimated from the $^{13}$CO emission), shows evidence of asymmetric infall, predominantly from the north and south. Close to the protostar, infall velocities appear to exceed free-fall velocities. 3D radiative transfer models, where the infall velocity is allowed to vary within the infall region, can explain the observed kinematics. The data suggests that a disk has started to form in B335 and that gas is falling towards that disk. However, kinematically-resolved line data towards the disk itself is needed to confirm the presence of a rotationally supported disk around this young protostar. The measured high infall velocities are not easily reconcilable with a magnetic braking scenario and suggest that there is a pressure gradient that allows the infall velocity to vary in the region.

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arXiv2023

JWST Peers into the Class I Protostar TMC1A: Atomic Jet and Spatially Resolved Dissociative Shock Region

Outflows and winds launched from young stars play a crucial role in the evolution of protostars and the early stages of planet formation. However, the specific details of the mechanism behind these phenomena, including how they affect the protoplanetary disk structure, are still debated. We present {\it JWST} NIRSpec Integral Field Unit (IFU) observations of atomic and H$_2$ lines from 1 -- 5.1 $\mu$m toward the low-mass protostar TMC1A. For the first time, a collimated atomic jet is detected from TMC1A in the [Fe II] line at 1.644 $\mu$m along with corresponding extended H$_2$ 2.12 $\mu$m emission. Towards the protostar, we detected spectrally broad H I and He I emissions with velocities up to 300 km/s that can be explained by a combination of protostellar accretion and a wide-angle wind. The 2$\mu$m continuum dust emission, H I, He I, and O I all show emission from the illuminated outflow cavity wall and scattered line emission. These observations demonstrate the potential of {\it JWST} to characterize and reveal new information about the hot inner regions of nearby protostars. In this case, a previously undetected atomic wind and ionized jet in a well-known outflow.

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arXiv2023

Triple spiral arms of a triple protostar system imaged in molecular lines

Most stars form in multiple star systems. For a better understanding of their formation processes, it is important to resolve the individual protostellar components and the surrounding envelope and disk material at the earliest possible formation epoch because the formation history can be lost in a few orbital timescales. Here we present the ALMA observational results of a young multiple protostellar system, IRAS 04239+2436, where three well-developed large spiral arms were detected in the shocked SO emission. Along the most conspicuous arm, the accretion streamer was also detected in the SO$_2$ emission. The observational results are complemented by numerical magneto-hydrodynamic simulations, where those large arms only appear in magnetically weakened clouds. The numerical simulations also suggest that the large triple spiral arms are the result of gravitational interactions between compact triple protostars and the turbulent infalling envelope.

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arXiv2023

A Large Double-ring Disk around the Taurus M Dwarf J04124068+2438157

Planet formation imprints signatures on the physical structures of disks. In this paper, we present high-resolution ($\sim$50 mas, 8 au) Atacama Large Millimeter/submillimeter Array (ALMA) observations of 1.3 mm dust continuum and CO line emission toward the disk around the M3.5 star 2MASS J04124068+2438157. The dust disk consists only of two narrow rings at radial distances of 0.47 and 0.78 arcsec ($\sim$70 and 116 au), with Gaussian $\sigma$ widths of 5.6 and 8.5 au, respectively. The width of the outer ring is smaller than the estimated pressure scale height by $\sim25\%$, suggesting dust trapping in a radial pressure bump. The dust disk size, set by the location of the outermost ring, is significantly larger (by $3\sigma$) than other disks with similar millimeter luminosity, which can be explained by an early formation of local pressure bump to stop radial drift of millimeter dust grains. After considering the disk's physical structure and accretion properties, we prefer planet--disk interaction over dead zone or photoevaporation models to explain the observed dust disk morphology. We carry out high-contrast imaging at $L'$ band using Keck/NIRC2 to search for potential young planets, but do not identify any source above $5\sigma$. Within the dust gap between the two rings, we reach a contrast level of $\sim$7 mag, constraining the possible planet below $\sim$2--4 $M_{\rm Jup}$. Analyses of the gap/ring properties suggest a $\sim$Saturn mass planet at $\sim$90 au is likely responsible for the formation of the outer ring, which can be potentially revealed with JWST.

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