Dust Trapping Research Articles

Constraints on the Physical Origin of Large Cavities in Transition Disks from Multiwavelength Dust Continuum Emission

The physical origin of the large cavities observed in transition disks is to date still unclear. Different physical mechanisms (e.g., a companion, dead zones, enhanced grain growth) produce disk cavities of different depth, and the expected spatial distribution of gas and solids in each mechanism is not the same. In this work, we analyze the multiwavelength interferometric visibilities of dust continuum observations obtained with Atacama Large Millimeter/submillimeter Array and Very Large Array for six transition disks: CQTau, UXTau A, LkCa15, RXJ1615, SR24S, and DMTau, and calculate brightness radial profiles, where diverse emission morphology is revealed at different wavelengths. The multiwavelength data are used to model the spectral energy distribution and compute constraints on the radial profile of the dust surface density, maximum grain size, and dust temperature in each disk. They are compared with the observational signatures expected from various physical mechanisms responsible for disk cavities. The observational signatures suggest that the cavities observed in the disks around UXTau A, LkCa15, and RXJ1615 could potentially originate from a dust trap created by a companion. Conversely, in the disks around CQTau, SR24S, DMTau, the origin of the cavity remains unclear, although it is compatible with a pressure bump and grain growth within the cavity.

Sulfur monoxide (SO) as a shock tracer in protoplanetary disks: Case of AB Aurigae

Context. Sulfur monoxide (SO) is known to be a good shock tracer in molecular clouds and protostar environments, but its abundance is difficult to reproduce, even with state-of-the-art astrochemical models. Aims. We investigate the properties of the observed SO emission in the protoplanetary disk of AB Auriga, a Herbig Ae star of 2.4 M⊙ in mass, located at 156 pc. The AB Aur system is unique because it exhibits a dust trap and at least one young putative planet orbiting at about 30 au from the central star. Methods. We reduced ALMA archival data (projects 2019.1.00579.S, 2021.1.00690.S, and 2021.1.01216.S) and analyzed the three detected SO lines (SO 65 − 54, 67 − 56 and 56 − 45). We also used C17O and C18O 2–1 data to complement the interpretation of the SO data. Results. For the three SO lines, the maximum SO emission in the ring is not located in the dust trap. Moreover, the inner radius of the SO ring is significantly larger than the CO emission inner radius, ∼160 au versus ∼90 au. The SO emission traces gas located in part beyond the dust ring. This emission likely originates from shocks at the interface of the outer spirals, observed in CO and scattered light emission, as well as those in the molecular and dust ring. Also, SO is detected within the cavity, at a radius of ∼20 − 30 au and with a rotation velocity compatible with the protoplanet P1. We speculate that this SO emission originates from accretion shocks onto the circumplanetary disk of the putative protoplanet P1. Conclusions. These observations confirm that SO is a good tracer of shocks in protoplanetary disks and could serve as a powerful new tool for detecting embedded (proto)planets.

A Dust-trapping Ring in the Planet-hosting Disk of Elias 2-24

Rings and gaps are among the most widely observed forms of substructure in protoplanetary disks. A gap–ring pair may be formed when a planet carves a gap in the disk, which produces a local pressure maximum following the gap that traps inwardly drifting dust grains and appears as a bright ring owing to the enhanced dust density. A dust-trapping ring would provide a promising environment for solid growth and possibly planetesimal production via the streaming instability. We present evidence of dust trapping in the bright ring of the planet-hosting disk Elias 2-24, from the analysis of 1.3 and 3 mm Atacama Large Millimeter/submillimeter Array observations at high spatial resolution (0.″029, 4.0 au). We leverage the high spatial resolution to demonstrate that larger grains are more efficiently trapped and place constraints on the local turbulence (8 × 10−4 < α turb < 0.03) and the gas-to-dust ratio (Σ g /Σ d < 30) in the ring. Using a scattering-included marginal probability analysis, we measure a total dust disk mass of Mdust=13.8−0.5+0.7×10−4M⊙ . We also show that at the orbital radius of the proposed perturber the gap is cleared of material down to a flux contrast of 10−3 of the peak flux in the disk.

From traffic jams to roadblocks: The outer regions of TW Hya with ALMA Band 8

Current ALMA surveys often underestimate protoplanetary disk sizes as many disks have extended low surface-brightness regions that fall below ALMA's detection limits. To effectively capture faint millimeter continuum emission in these outer regions, increased sensitivity is required. In order to gain insights on the connection between disk structure and planet formation, we aim to uncover continuum emission in the outer regions of the disk around TW Hya. Additionally, we aim to investigate the evolution of this disk by studying its dust properties. We present Atacama Large Millimeter Array (ALMA) observations of TW Hya at 0.65 mm with sim 0.5 arcsecond angular resolution, together with high angular resolution archival observations at 0.87 mm, 1.3 mm, 2.1 mm and 3.1 mm. We constrain the outer disk emission with both image-plane retrieval, and visibility-plane modeling with non-parametric and parametric fitting tools. Our results confirm emission in the outer disk regions of TW Hya (60 au leq R leq 110 au) at 0.65 mm, 0.87 mm and 1.3 mm. With image-plane retrieval we resolve the new continuum gap and ring, namely D79 and B86, at 0.87 mm and 1.3 mm. With visibility-plane modeling we also detect this substructure at 0.65 mm in the form of a quasi-constant emission at the 1sigma level Furthermore, it has a high spectral index of 3.7, which may indicate dust grain sizes ll 1 mm. It may be a dust trap or a traffic jam, that has a flux density of sim 60 mJy and a mass (1.59 $M_ that accounts for up to 2&lt;!PCT!&gt; of the dust disk at 0.65 mm. We confirm the existence of a faint ring in the outer regions of TW Hya at multiple millimeter wavelengths. With visibility-plane modeling, we are able to set constrains that are 3 times better than the resolution of our Band 8 observations.

Supersonic coaxial aerodynamic atomization dust removal technology

The high concentration of respirable dust pollution created during coal mining has long been known to be harmful to employee health. A water absorbing atomization device has certain advantages when spray trapping particle sizes of PM2.5–10. To further improve the PM0–2.5 trapping efficiency, supersonic coaxial pneumatic atomization dust removal technology has been developed. The effects of fog droplet characteristics on the instantaneous diffusion of dust were studied by numerical simulation and macro- and microexperiments for the first time, and the coupling characteristics of fog droplets and dust fields were obtained. The results show that with increasing aerodynamic pressure, the supersonic range extends along the axis toward the nozzle outlet, and the average velocity in the tube increases. Under different pressures, the droplet particle size in the supersonic coaxial atomizing nozzle is <6 μm and decreases with increasing aerodynamic pressure. When a droplet effuses from the nozzle, the transonic distribution of the flow field causes the droplet velocity to increase first and then decrease under the drag force. The droplet field characteristic distribution of supersonic coaxial atomization is determined by droplet evaporation, condensation, and migration. Under the same pressure, with increasing spray distance, the distribution of the droplet particle size increases in a stepwise manner, and the droplet velocity decreases according to an exponential function so that the droplet field produces a high-speed fine fog area. The range of droplets with higher velocities and smaller particle sizes is mainly influenced by migration and increases with increasing pressure. The coupling effect droplet field and dust field can be characterized by the instantaneous dispersion of dust and are determined by the distribution characteristics of the fog droplet field. The large range of high-speed fine fog produced by supersonic coaxial atomization technology easily traps respirable dust, and the classification efficiency of PM0–2.5 reaches 90%. In this study, a new dynamic microfog dust trapping technique was proposed, and a new method of instantaneous sampling combined with a microscopic dispersion test was adopted to characterize the temporal and spatial distributions of dust fields affected by fog droplet fields, reveal the generation of dynamic microfog and the mechanism of dust trapping, enrich the theory of fine dust trapping, and provide technical support for the safe production and utilization of coal.

Pendekatan Model Causal Loop Diagram (CLD) Pada Pengelolaan Air Limbah PT.Chandra Asri Petrochemical

The development of industries linked to population growth in Indonesia has led to increased waste production, particularly in terms of wastewater. This research examines the wastewater management system at PT. Chandra Asri Petrochemical Tbk (CAP), emphasizes the importance of waste treatment to prevent environmental pollution and maintain ecosystem sustainability. Through literature review methods, field studies, and the utilization of a simulation model employing Causal Loop Diagrams (CLD), this study evaluates the impact of industrial wastewater management on the environment and society. The research findings identify wastewater treatment processes at CAP, including the Neutralization Pit, Oil Separator, Dust Filter, and Dust Trap, along with regular inspections to ensure that water quality meets the established standards. Keywords: Causal Loop Diagrams, Dynamic Methods, Environmental Impact, Waste Water Quality Standards, Waste Water Treatment.

An ALMA Molecular Inventory of Warm Herbig Ae Disks. II. Abundant Complex Organics and Volatile Sulphur in the IRS 48 Disk

The Atacama Large Millimeter/submillimeter Array (ALMA) can probe the molecular content of planet-forming disks with unprecedented sensitivity. These observations allow us to build up an inventory of the volatiles available for forming planets and comets. Herbig Ae transition disks are fruitful targets due to the thermal sublimation of complex organic molecules (COMs) and likely H2O-rich ices in these disks. The IRS 48 disk shows a particularly rich chemistry that can be directly linked to its asymmetric dust trap. Here, we present ALMA observations of the IRS 48 disk where we detect 16 different molecules and make the first robust detections of H213CO , 34SO, 33SO, and c-H2COCH2 (ethylene oxide) in a protoplanetary disk. All of the molecular emissions, aside from CO, are co-located with the dust trap, and this includes newly detected simple molecules such as HCO+, HCN , and CS. Interestingly, there are spatial offsets between different molecular families, including between the COMs and sulfur-bearing species, with the latter being more azimuthally extended and radially located further from the star. The abundances of the newly detected COMs relative to CH3OH are higher than the expected protostellar ratios, which implies some degree of chemical processing of the inherited ices during the disk lifetime. These data highlight IRS 48 as a unique astrochemical laboratory to unravel the full volatile reservoir at the epoch of planet and comet formation and the role of the disk in (re)setting chemical complexity.

Turbulent Vortex with Moderate Dust Settling Probed by Scattering-induced Polarization in the IRS 48 System

We investigate the crescent-shaped dust trap in the transition disk Oph IRS 48 using well-resolved (sub)millimeter polarimetric observations at ALMA Band 7 (870 μm). The dust polarization map reveals patterns consistent with dust-scattering-induced polarization. There is a relative displacement between the polarized flux and the total flux, which holds the key to understanding the dust scale heights in this system. We model the polarization observations, focusing on the effects of dust scale heights. We find that the interplay between the inclination-induced polarization and the polarization arising from radiation anisotropy in the crescent determines the observed polarization; the anisotropy is controlled by the dust optical depth along the midplane, which is, in turn, determined by the dust scale height in the vertical direction. We find that the dust grains can be neither completely settled nor well mixed with the gas. The completely settled case produces little radial displacement between the total and polarized flux, while the well-mixed case produces an azimuthal pattern in the outer (radial) edge of the crescent that is not observed. Our best model has a gas-to-dust scale height ratio of 2 and can reproduce both the radial displacement and the azimuthal displacement between the total and polarized flux. We infer an effective turbulence α parameter of approximately 0.0001–0.005. The scattering-induced polarization provides insight into a turbulent vortex with a moderate level of dust settling in the IRS 48 system, which is hard to achieve otherwise.

The role of drag and gravity on dust concentration in a gravitationally unstable disc

ABSTRACT We carry out three-dimensional smoothed particle hydrodynamics simulations to study the role of gravitational and drag forces on the concentration of large dust grains (St &amp;gt; 1) in the spiral arms of gravitationally unstable protoplanetary discs, and the resulting implications for planet formation. We find that both drag and gravity play an important role in the evolution of large dust grains. If we include both, grains that would otherwise be partially decoupled will become well coupled and trace the spirals. For the dust grains most influenced by drag (with Stokes numbers near unity), the dust disc quickly becomes gravitationally unstable and rapidly forms clumps with masses between 0.15–6M⊕. A large fraction of clumps are below the threshold where runaway gas accretion can occur. However, if dust self-gravity is neglected, the dust is unable to form clumps, despite still becoming trapped in the gas spirals. When large dust grains are unable to feel either gas gravity or drag, the dust is unable to trace the gas spirals. Hence, full physics is needed to properly simulate dust in gravitationally unstable discs. Dust trapping of large grains in spiral arms of discs stable to gas fragmentation could explain planet formation in very young discs by a population of planetesimals formed due to the combined roles of drag and gravity in the earliest stages of a disc’s evolution. Furthermore, it highlights that gravitationally unstable discs are not just important for forming gas giants quickly, it can also rapidly form Earth mass bodies.

THRESHOLD EFFECT IN DUSTY CLUSTERS IN A MAGNETIC FIELD

The process of occurrence of rotational motion of dusty plasma in a longitudinal magnetic field was investigated. It was experimentally found that the occurrence of rotation depends on the number of dust particles in the direction perpendicular to the magnetic induction vector, as well as on their vertical position in the dust trap (i.e., the magnitude of the electric field). The value of the threshold for the appearance of rotation in the magnetic field at a constant number of particles depends on the particle size and discharge conditions. The parameters of the experiment are selected, at which the effect manifests itself in detail. It has been established that for stationary rotation, a stable position of dust particles in the cross section is required, which corresponds to the filling of the shells of a rotating dust structure.

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 observations of a large asymmetric dusty ring around the M-type star CIDA 9A. We detect a dust asymmetry in both 1.3 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-resolution 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.

Impact of Sisal Fiber &amp; Coil Fiber with Coconut Coil in The Stone Grid Aggregate Physical Properties

Bituminous substantial blends are the essential layer used commonly in Versatile pavements. The property of bituminous mixes can be improved by extension of fibers like coir strands. Fiber lengths were saved for instance 10mm, 15mm and 20mm and used at the speed of 0.3%, 0.5% and 0.7% by weight of mix. This paper gives a review of including Sisal fiber and Coir fiber as added substances in bituminous mix concrete. The utilization of sisal fiber moreover, coir fiber animates better, strength and impedes from channel down of the blend. The wire of fiber in the mix work on the mechanical properties. In India around 8 lakh heaps of coir fiber being made and used various outcomes, the extra waste fiber dumped in open land causing serious normal pollution. Along these lines, a survey has been embraced to involve the waste fiber as help in bituminous concrete. Sisal Fiber with low upkeep and irrelevantly extreme and recyclable mileage. The external forefront removes the sisal fiber that disposes of the crush from inside the plaid herringbone and fine fibers are open. Sisal is against static and will not easily ingest water or suddenness and doesn't attract dust particles or trap them. This paper shows the impact of sisal fiber with loop fiber on bituminous substantial blend.

Millimeter emission in photoevaporating disks is determined by early substructures

Context. Photoevaporation and dust-trapping are individually considered to be important mechanisms in the evolution and morphology of protoplanetary disks. However, it is not yet clear what kind of observational features are expected when both processes operate simultaneously. Aims. We studied how the presence (or absence) of early substructures, such as the gaps caused by planets, affects the evolution of the dust distribution and flux in the millimeter continuum of disks that are undergoing photoevaporative dispersal. We also tested if the predicted properties resemble those observed in the population of transition disks. Methods. We used the numerical code Dustpy to simulate disk evolution considering gas accretion, dust growth, dust-trapping at substructures, and mass loss due to X-ray and EUV (XEUV) photoevaporation and dust entrainment. Then, we compared how the dust mass and millimeter flux evolve for different disk models. Results. We find that, during photoevaporative dispersal, disks with primordial substructures retain more dust and are brighter in the millimeter continuum than disks without early substructures, regardless of the photoevaporative cavity size. Once the photoevaporative cavity opens, the estimated fluxes for the disk models that are initially structured are comparable to those found in the bright transition disk population (Fmm &gt; 30 mJy), while the disk models that are initially smooth have fluxes comparable to the transition disks from the faint population (Fmm &lt; 30 mJy), suggesting a link between each model and population. Conclusions. Our models indicate that the efficiency of the dust trapping determines the millimeter flux of the disk, while the gas loss due to photoevaporation controls the formation and expansion of a cavity, decoupling the mechanisms responsible for each feature. In consequence, even a planet with a mass comparable to Saturn could trap enough dust to reproduce the millimeter emission of a bright transition disk, while its cavity size is independently driven by photoevaporative dispersal.

Double Dust Structures in Different Stratum Phases in Moderate Magnetic Fields

Three-dimensional plasma-dust formations consisting of calibrated dust particles differing in sizes and material densities are studied. The characteristic features of the structures formation in stratified glow discharge were studied, as well as their shapes and dynamics in the external magnetic fields. From several types of powders, the spatially separated double structures were obtained, which filled the dust trap, being located in different stratum phases. For each part of the structure, the average rotational velocities were obtained as functions of the magnetic field. In the range, in which the rotation mechanism depends on the particle size and the ion drag force is dominant, the rotational velocity was numerically estimated with allowance for the parameters variation along the stratum.

The Effect of Dust Evolution and Traps on Inner Disk Water Enrichment

Abstract Substructures in protoplanetary disks can act as dust traps that shape the radial distribution of pebbles. By blocking the passage of pebbles, the presence of gaps in disks may have a profound effect on pebble delivery into the inner disk, crucial for the formation of inner planets via pebble accretion. This process can also affect the delivery of volatiles (such as H2O) and their abundance within the water snow line region (within a few au). In this study, we aim to understand what effect the presence of gaps in the outer gas disk may have on water vapor enrichment in the inner disk. Building on previous work, we employ a volatile-inclusive disk evolution model that considers an evolving ice-bearing drifting dust population, sensitive to dust traps, which loses its icy content to sublimation upon reaching the snow line. We find that the vapor abundance in the inner disk is strongly affected by the fragmentation velocity (v f) and turbulence, which control how intense vapor enrichment from pebble delivery is, if present, and how long it may last. Generally, for disks with low to moderate turbulence (α ≤ 1 × 10−3) and a range of v f, radial locations and gap depths (especially those of the innermost gaps) can significantly alter enrichment. Shallow inner gaps may continuously leak material from beyond it, despite the presence of additional deep outer gaps. We finally find that for realistic v f (≤10 m s−1), the presence of gaps is more important than planetesimal formation beyond the snow line in regulating pebble and volatile delivery into the inner disk.

Bioaccumulation of potentially toxic elements by indigenous and exotic trees growing around a copper leaching plant in Mufulira, Zambia

Potentially toxic elements (PTEs) from mining industries pollute the surrounding environment and threaten the health of communities. Worldwide, exotic and indigenous trees are being recommended for green belts to trap dust and thereby limit the dispersion of PTEs. This study compares the potential of exotic (Eucalyptus grandis and E. camaldulensis) and native (Brachystegia longifolia) tree species in Zambia to accumulate PTEs and evaluate their ability to biomonitor heavy metal pollution. Tree bark and leaf samples were collected from 10 trees per study species growing at the same site downwind from a copper-leaching plant. Thirty topsoil samples were collected one metre from each sampled tree trunk. Portable X-ray fluorescence was used to analyse the elemental composition and concentration of trace elements in plant and soil samples. Pollution indices were used to establish the status and degree of soil contamination, while the bioaccumulation factor determined the ability of the studied species to accumulate PTEs. Heavy metals, including Mn, Ni, Pb, Cd, Cu, Fe and Zn were detected across soil and biomass samples, with a significant variation between species and plant parts. The pollution indices established that the soil at the study site is highly contaminated with Cu. The concentration of the studied trace elements varied across species following the order E. grandis > B. longifolia > E. camaldulensis in both tree bark and leaves. Determined bioaccumulation factors indicated Cd, Mn and Zn accumulation abilities of all the studied species suggesting their biomonitoring and phytoremediation potential. This implies that the study species have the potential to biomonitor Cd, Mn and Zn. Furthermore, a higher concentration of Cu was detected in B. longifolia bark, suggesting that this tree species can be used to biomonitor Cu pollution attributed to emissions from industrial activities. This study presents new insights into improving the management of polluted environments through biomonitoring and bioaccumulation of PTEs which can guide the selection of appropriate species for greenbelts in industrial areas.

Formation of lawn grasses on the basis of soil conservation in the park zone of VNAU

The conducted research is devoted to biodiversity, namely soil conservation. The very use of lawn grasses as an integral aesthetic decorative element of landscape design is at the same time an ecological and ameliorating factor of influence on the surrounding natural environment, which is quite widely used not only in Ukraine, but also abroad. It has been established that a feature of improving the condition of lawn cultural phytocenoses is the use of low-lying perennial grasses and their varieties, which are maximally adapted to the edapho-climatic conditions of the Podillia zone. Dense lawn coverings trap dust, increase air humidity, improve the microclimate of the environment due to the phytoncides released by them, thereby improving the air, preventing erosion and improving the agrophysical properties of the soil. Based on the records and observations made in the conditions of the park zone of the Vinnytsia National Agrarian University, the composition of lawn grass mixtures, quality condition and density of the lawn were established. The economic and ecobiological structure of lawns is displayed. The peculiarities of the formation of lawn cultural phytocenoses based on the analysis of the qualitative state of the existing grass stand are given. The percentage ratio of the quality composition of lawn grasses has been established. The agrotechnical measures for the care of lawn cultural phytocenoses at the research site are scientifically substantiated. A summarized balance of lawn areas by quality condition is given, which makes it possible to reasonably approach the planning of agrotechnical measures.

Three-dimensional Orbit of AC Her Determined: Binary-induced Truncation Cannot Explain the Large Cavity in This Post-AGB Transition Disk

Some evolved binaries, namely post–asymptotic giant branch (AGB) binaries, are surrounded by stable and massive circumbinary disks similar to protoplanetary disks found around young stars. Around 10% of these disks are transition disks: they have a large inner cavity in the dust. Previous interferometric measurements and modeling have ruled out these cavities being formed by dust sublimation and suggested that they are due to massive circumbinary planets that trap dust in the disk and produce the observed depletion of refractory elements on the surfaces of the post-AGB stars. In this study, we test an alternative scenario in which the large cavities could be due to dynamical truncation from the inner binary. We performed near-infrared interferometric observations with the CHARA Array on the archetype of such a transition disk around a post-AGB binary: AC Her. We detect the companion at ten epochs over 4 yr and determine the three-dimensional orbit using these astrometric measurements in combination with a radial velocity time series. This is the first astrometric orbit constructed for a post-AGB binary system. We derive the best-fit orbit with a semimajor axis of 2.01 ± 0.01 mas (2.83 ± 0.08 au), inclination (142.9 ± 1.1)°, and longitude of the ascending node (155.1 ± 1.8)°. We find that the theoretical dynamical truncation and dust sublimation radii are at least ∼3× smaller than the observed inner disk radius (∼21.5 mas or 30 au). This strengthens the hypothesis that the origin of the cavity is due to the presence of a circumbinary planet.

Meridional circulation driven by planetary spiral wakes in radiative and magnetized protoplanetary discs

ABSTRACT We study a Jupiter-mass planet formation for the first time in radiative magnetohydrodynamics (MHD) simulations and compare it with pure hydrodynamical simulations, and also with different isothermal configurations. We found that the meridional circulation is the same in every set-up. The planetary spiral wakes drive a vertical stirring inside the protoplanetary disc and the encounter with these shock fronts also helps in delivering gas vertically on to the Hill sphere. The accretion dynamics are unchanged: the planet accretes vertically, and there is outflow in the mid-plane regions inside the Hill sphere. We determined the effective α-viscosity generated in the disc by the various angular momentum loss mechanisms, which showed that magnetic fields produce high turbulence in the ideal MHD limit, and grows from α ∼ 10−2.5 up to ∼10−1.5 after the planet spirals develop. In the HD simulations, the planetary spirals contribute to α ∼ 10−3, making this a very important angular momentum transport mechanism. Due to the various α values in the different set-ups, the gap opening is different in each case. In the radiative MHD set-ups, the high turbulent viscosity prevents gap opening, leading to a higher Hill mass, and no clear dust trapping regions. While the Hill accretion rate is $10^{-6}~ \rm {M_{Jup}\,yr^{-1}}$ in all set-ups, the accretion variability is orders of magnitude higher in radiative runs than in isothermal ones. Finally, with higher resolution runs, the magnetorotational instability started to be resolved, changing the effective viscosity and increasing the heating in the disc.

A major asymmetric ice trap in a planet-forming disk

Context. Most well-resolved disks observed with the Atacama Large Millimeter/submillimeter Array (ALMA) show signs of dust traps. These dust traps set the chemical composition of the planet-forming material in these disks, as the dust grains with their icy mantles are trapped at specific radii and could deplete the gas and dust at smaller radii of volatiles. Aims. In this work, we analyse the first detection of nitric oxide (NO) in a protoplanetary disk. We aim to constrain the nitrogen chemistry and the gas-phase C/O ratio in the highly asymmetric dust trap in the Oph-IRS 48 disk. Methods. We used ALMA observations of NO, CN, C2H, and related molecules in the Oph-IRS 48 disk. We modeled the effect of the increased dust-to-gas ratio in the dust trap on the physical and chemical structure using a dedicated nitrogen chemistry network in the thermochemical code DALI. Furthermore, we explored how ice sublimation contributes to the observed emission lines. Finally, we used the model to put constraints on the nitrogen-bearing ices. Results. Nitric oxide (NO) is only observed at the location of the dust trap, but CN and C2H are not detected in the Oph-IRS 48 disk. This results in an CN/NO column density ratio of &lt;0.05 and thus a low C/O ratio at the location of the dust trap. Models show that the dust trap cools the disk midplane down to ~30 K, just above the NO sublimation temperature of ~25 K. The main gas-phase formation pathways to NO though OH and NH in the fiducial model predict NO emission that is an order of magnitude lower than what has been observed. The gaseous NO column density can be increased by factors ranging from 2.8 to 10 when the H2O and NH3 gas abundances are significantly boosted by ice sublimation. However, these models are inconsistent with the upper limits on the H2O and OH column densities derived from Herschel PACS observations and the upper limit on CN derived from ALMA observations. As the models require an additional source of NO to explain its detection, the NO seen in the observations is likely the photodissociation product of a larger molecule sublimating from the ices. The non-detection of CN provides a tighter constraint on the disk C/O ratio than the C2H upper limit. Conclusions. We propose that the NO emission in the Oph-IRS 48 disk is closely related to the nitrogen-bearing ices sublimating in the dust trap. The non-detection of CN constrains the C/O ratio both inside and outside the dust trap to be &lt;1 if all nitrogen initially starts as N2 and ≤ 0.6, consistent with the Solar value, if (at least part of) the nitrogen initially starts as N or NH3.