scholarly journals Multi-wavelength observations of protoplanetary discs as a proxy for the gas disc mass

2019 ◽  
Author(s):  
B Veronesi ◽  
G Lodato ◽  
G Dipierro ◽  
E Ragusa ◽  
C Hall ◽  
...  
Keyword(s):  
Surface Density ◽  
Scattered Light ◽  
Stopping Time ◽  
Stokes Number ◽  
Continuum Emission ◽  
Gravitational Perturbation ◽  
Multi Wavelength ◽  
Hydrodynamical Modelling ◽  
Small Dust ◽  
Protoplanetary Discs

Abstract Recent observations of protoplanetary discs reveal disc substructures potentially caused by embedded planets. We investigate how the gas surface density in discs changes the observed morphology in scattered light and dust continuum emission. Assuming that disc substructures are due to embedded protoplanets, we combine hydrodynamical modelling with radiative transfer simulations of dusty protoplanetary discs hosting planets. The response of different dust species to the gravitational perturbation induced by a planet depends on the drag stopping time — a function of the generally unknown local gas density. Small dust grains, being stuck to the gas, show spirals. Larger grains decouple, showing progressively more axisymmetric (ring-like) substructure as decoupling increases with grain size or with the inverse of the gas disc mass. We show that simultaneous modelling of scattered light and dust continuum emission is able to constrain the Stokes number, St. Hence, if the dust properties are known, this constrains the local gas surface density, Σgas, at the location of the structure, and hence the total gas mass. In particular, we found that observing ring-like structures in mm-emitting grains requires St ≳ 0.4 and therefore Σgas ≲ 0.4 g/cm2. We apply this idea to observed protoplanetary discs showing substructures both in scattered light and in the dust continuum.

scholarly journals Dust-driven viscous ring-instability in protoplanetary disks

2018 ◽  
Vol 609 ◽  
pp. A50 ◽  
Author(s):  
C. P. Dullemond ◽  
A. B. T. Penzlin
Keyword(s):  
Surface Density ◽  
Scattered Light ◽  
Protoplanetary Disks ◽  
Continuum Emission ◽  
Rotational Instability ◽  
Local Pressure ◽  
Ionization Degree ◽  
Local Maxima ◽  
Gas Ionization ◽  
Small Dust

Protoplanetary disks often appear as multiple concentric rings in dust continuum emission maps and scattered light images. These features are often associated with possible young planets in these disks. Many non-planetary explanations have also been suggested, including snow lines, dead zones and secular gravitational instabilities in the dust. In this paper we suggest another potential origin. The presence of copious amounts of dust tends to strongly reduce the conductivity of the gas, thereby inhibiting the magneto-rotational instability, and thus reducing the turbulence in the disk. From viscous disk theory it is known that a disk tends to increase its surface density in regions where the viscosity (i.e. turbulence) is low. Local maxima in the gas pressure tend to attract dust through radial drift, increasing the dust content even more. We have investigated mathematically if this could potentially lead to a feedback loop in which a perturbation in the dust surface density could perturb the gas surface density, leading to increased dust drift and thus amplification of the dust perturbation and, as a consequence, the gas perturbation. We find that this is indeed possible, even for moderately small dust grain sizes, which drift less efficiently, but which are more likely to affect the gas ionization degree. We speculate that this instability could be triggered by the small dust population initially, and when the local pressure maxima are strong enough, the larger dust grains get trapped and lead to the familiar ring-like shapes. We also discuss the many uncertainties and limitations of this model.

scholarly journals Observable scattered light features from inclined and non-inclined planets embedded in protoplanetary discs

2019 ◽  
Vol 487 (4) ◽  
pp. 5372-5387
Author(s):  
Dylan L Kloster ◽  
M Flock
Keyword(s):  
Surface Density ◽  
Scattered Light ◽  
Intensity Variation ◽  
Theoretical Models ◽  
Upper Atmosphere ◽  
High Mass ◽  
Hydrodynamic Simulations ◽  
3D Simulations ◽  
2D And 3D ◽  
Protoplanetary Discs

ABSTRACT Over the last few years instruments such as VLT/SPHERE and Subaru/HiCIAO have been able to take detailed scattered light images of protoplanetary discs. Many of the features observed in these discs are generally suspected to be caused by an embedded planet, and understanding the cause of these features requires detailed theoretical models. In this work we investigate disc–planet interactions using the pluto code to run 2D and 3D hydrodynamic simulations of protoplanetary discs with embedded 30 and 300 M⊕ planets on both an inclined (i = 2.86°) and non-inclined orbit, using an α-viscosity of 4 × 10−3. We produce synthetic scattered light images of these discs at H-band wavelengths using the radiative transfer code radmc3d. We find that while the surface density evolution in 2D and 3D simulations of inclined and non-inclined planets remain fairly similar, their observational appearance is remarkably different. Most of the features seen in the synthetic H-band images are connected to density variations of the disc at around 3.3 scale heights above and below the mid-plane, which emphasizes the need for 3D simulations. Planets on sustained orbital inclinations disrupt the disc’s upper atmosphere and produce radically different observable features and intensity profiles, including shadowing effects and intensity variation of the order of 10–20 times the surrounding background. The vertical optical depth to the disc mid-plane for H-band wavelengths is τ ≈ 20 in the disc gap created by the high-mass planet. We conclude that direct imaging of planets embedded in the disc remains difficult to observe, even for massive planets in the gap.

scholarly journals Observational signatures of eccentric Jupiters inside gas cavities in protoplanetary discs

2021 ◽  
Author(s):  
Clément Baruteau ◽  
Gaylor Wafflard-Fernandez ◽  
Romane Le Gal ◽  
Florian Debras ◽  
Andrés Carmona ◽  
...  
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Scattered Light ◽  
Dust Emission ◽  
Three Dimensional ◽  
Continuum Emission ◽  
Integrated Intensity ◽  
Gas Cavity ◽  
Hydrodynamical Simulations ◽  
Small Dust

Abstract Predicting how a young planet shapes the gas and dust emission of its parent disc is key to constraining the presence of unseen planets in protoplanetary disc observations. We investigate the case of a 2 Jupiter mass planet that becomes eccentric after migrating into a low-density gas cavity in its parent disc. Two-dimensional hydrodynamical simulations are performed and post-processed by three-dimensional radiative transfer calculations. In our disc model, the planet eccentricity reaches ∼0.25, which induces strong asymmetries in the gas density inside the cavity. These asymmetries are enhanced by photodissociation and form large-scale asymmetries in 12CO J=3→2 integrated intensity maps. They are shown to be detectable for an angular resolution and a noise level similar to those achieved in ALMA observations. Furthermore, the planet eccentricity renders the gas inside the cavity eccentric, which manifests as a narrowing, stretching and twisting of iso-velocity contours in velocity maps of 12CO J=3→2. The planet eccentricity does not, however, give rise to detectable signatures in 13CO and C18O J=3→2 inside the cavity because of low column densities. Outside the cavity, the gas maintains near-circular orbits, and the vertically extended optically thick CO emission displays a four-lobed pattern in integrated intensity maps for disc inclinations $\gtrsim$ 30○. The lack of large and small dust inside the cavity in our model further implies that synthetic images of the continuum emission in the sub-millimetre, and of polarized scattered light in the near-infrared, do not show significant differences when the planet is eccentric or still circular inside the cavity.

scholarly journals Evidence for a massive dust-trapping vortex connected to spirals

2018 ◽  
Vol 619 ◽  
pp. A161 ◽  
Author(s):  
P. Cazzoletti ◽  
E. F. van Dishoeck ◽  
P. Pinilla ◽  
M. Tazzari ◽  
S. Facchini ◽  
...  
Keyword(s):  
Large Scale ◽  
Scattered Light ◽  
Continuum Emission ◽  
Asymmetric Structure ◽  
Outer Planet ◽  
Dust Trapping ◽  
Spiral Arms ◽  
Multi Wavelength ◽  
The Asymmetry ◽  
Dust Distribution

Context. Spiral arms, rings and large scale asymmetries are structures observed in high resolution observations of protoplanetary disks, and it appears that some of the disks showing spiral arms in scattered light also show asymmetries in millimeter-sized dust. HD 135344B is one such disk. Planets are invoked as the origin of these structures, but no planet has been observed so far and upper limits are becoming more stringent with time. Aims. We want to investigate the nature of the asymmetric structure in the HD 135344B disk in order to understand the origin of the spirals and of the asymmetry seen in this disk. Ultimately, we aim to understand whether or not one or more planets are needed to explain such structures. Methods. We present new ALMA sub-0.1′′ resolution observations at optically thin wavelengths (λ = 2.8 and 1.9 mm) of the HD 135344B disk. The high spatial resolution allows us to unambiguously characterize the mm-dust morphology of the disk. The low optical depth of continuum emission probes the bulk of the dust content of the vortex. Moreover, we have combined the new observations with archival data at shorter wavelengths to perform a multi-wavelength analysis and to obtain information about the dust distribution and properties inside the observed asymmetry. Results. We resolve the asymmetric disk into a symmetric ring + asymmetric crescent, and observe that (1) the spectral index strongly decreases at the centre of the vortex, consistent with the presence of large grains; (2) for the first time, an azimuthal shift of the peak of the vortex with wavelength is observed; (3) the azimuthal width of the vortex decreases at longer wavelengths, as expected for dust traps. These features allow confirming the nature of the asymmetry as a vortex. Finally, under the assumption of optically thin emission, a lower limit to the total mass of the vortex is 0.3MJupiter. Considering the uncertainties involved in this estimate, it is possible that the actual mass of the vortex is higher and possibly within the required values (~4 MJupiter) to launch spiral arms similar to those observed in scattered light. If this is the case, then explaining the morphology does not require an outer planet.

scholarly journals Non-Keplerian spirals, a gas-pressure dust trap, and an eccentric gas cavity in the circumbinary disc around HD 142527

2021 ◽  
Vol 504 (1) ◽  
pp. 782-791
Author(s):  
H Garg ◽  
C Pinte ◽  
V Christiaens ◽  
D J Price ◽  
J S Lazendic ◽  
...  
Keyword(s):  
Surface Density ◽  
Angular Resolution ◽  
Stokes Number ◽  
Continuum Emission ◽  
Vertical Temperature ◽  
Dust Trap ◽  
Density Peaks ◽  
Density Maps ◽  
Gas Cavity ◽  
Spiral Structures

ABSTRACT We present ALMA observations of the 12CO, 13CO, C18O J = 2-1 transitions and the 1.3 mm continuum emission for the circumbinary disc around HD 142527, at an angular resolution of ≈ 0${_{.}^{\prime\prime}}$3. We observe multiple spiral structures in intensity, velocity, and velocity dispersion for the 12CO and 13CO gas tracers. A newly detected 12CO spiral originates from the dust horseshoe, and is rotating at super-Keplerian velocity or vertically ascending, whilst the interspiral gas is rotating at sub-Keplerian velocities. This new spiral possibly connects to a previously identified spiral, thus spanning >360°. A spatial offset of  30 au is observed between the 12CO and 13CO spirals, to which we hypothesize that the gas layers are propagating at different speeds (surfing) due to a non-zero vertical temperature gradient. Leveraging the varying optical depths between the CO isotopologues, we reconstruct temperature and column density maps of the outer disc. Gas surface density peaks at r ≈ 180 au, coincident with the peak of continuum emission. Here, the dust grains have a Stokes number of ≈ 1, confirming radial and azimuthal trapping in the horseshoe. We measure a cavity radius at half-maximum surface density of ≈ 100 au, and a cavity eccentricity between 0.3 and 0.45.

scholarly journals Inferring giant planets from ALMA millimeter continuum and line observations in (transition) disks

2018 ◽  
Vol 612 ◽  
pp. A104 ◽  
Author(s):  
S. Facchini ◽  
P. Pinilla ◽  
E. F. van Dishoeck ◽  
M. de Juan Ovelar
Keyword(s):  
Surface Density ◽  
Scattered Light ◽  
Temperature Drop ◽  
Line Emission ◽  
Continuum Emission ◽  
Rotational Line ◽  
Gas Temperature ◽  
Hydrodynamical Simulations ◽  
Dust Evolution ◽  
Transition Disks

Context. Radial gaps or cavities in the continuum emission in the IR-mm wavelength range are potential signatures of protoplanets embedded in their natal protoplanetary disk are. Hitherto, models have relied on the combination of mm continuum observations and near-infrared scattered light images to put constraints on the properties of embedded planets. Atacama Large Millimeter/submillimeter Array (ALMA) observations are now probing spatially resolved rotational line emission of CO and other chemical species. These observations can provide complementary information on the mechanism carving the gaps in dust and additional constraints on the purported planet mass. Aims. We investigate whether the combination of ALMA continuum and CO line observations can constrain the presence and mass of planets embedded in protoplanetary disks. Methods. We post-processed azimuthally averaged 2D hydrodynamical simulations of planet-disk models, in which the dust densities and grain size distributions are computed with a dust evolution code that considers radial drift, fragmentation, and growth. The simulations explored various planet masses (1 MJ ≤ Mp ≤ 15 MJ) and turbulent parameters (10−4 ≤ α ≤ 10−3). The outputs were then post-processed with the thermochemical code DALI, accounting for the radially and vertically varying dust properties. We obtained the gas and dust temperature structures, chemical abundances, and synthetic emission maps of both thermal continuum and CO rotational lines. This is the first study combining hydrodynamical simulations, dust evolution, full radiative transfer, and chemistry to predict gas emission of disks hosting massive planets. Results. All radial intensity profiles of 12CO, 13CO, and C18O show a gap at the planet location. The ratio between the location of the gap as seen in CO and the peak in the mm continuum at the pressure maximum outside the orbit of the planet shows a clear dependence on planet mass and is independent of disk viscosity for the parameters explored in this paper. Because of the low dust density in the gaps, the dust and gas components can become thermally decoupled and the gas becomes colder than the dust. The gaps seen in CO are due to a combination of gas temperature dropping at the location of the planet and of the underlying surface density profile. Both effects need to be taken into account and disentangled when inferring gas surface densities from observed CO intensity profiles; otherwise, the gas surface density drop at the planet location can easily be overestimated. CO line ratios across the gap are able to quantify the gas temperature drop in the gaps in observed systems. Finally, a CO cavity not observed in any of the models, only CO gaps, indicating that one single massive planet is not able to explain the CO cavities observed in transition disks, at least without additional physical or chemical mechanisms.

scholarly journals Dust dynamics in planet-driven spirals

2020 ◽  
Vol 643 ◽  
pp. A92
Author(s):  
J. A. Sturm ◽  
G. P. Rosotti ◽  
C. Dominik
Keyword(s):  
Analytical Model ◽  
Gas Dynamics ◽  
Surface Density ◽  
Scattered Light ◽  
Stokes Number ◽  
Dust Dynamics ◽  
The Difference ◽  
Underlying Mechanisms ◽  
Continuum Data ◽  
The Continuum

Context. Protoplanetary disks are known to host spiral features that are observed in scattered light, the ALMA continuum, and more recently in CO gas emission and gas dynamics. However, it is unknown whether spirals in gas and dust trace the same morphology. Aims. We aim to study the morphology and amplitude of dusty spirals as function of the Stokes number and the underlying mechanisms that cause a difference between dusty spirals and gas spirals. We then construct a model to relate the deviation from Keplerian rotation in the gas to a perturbation in surface density of the gas and dust. Methods. We used FARGO-3D with dust implementation to numerically study the spirals, after which the results were interpreted using a semi-analytical model. This model was tested on observational data to predict the perturbation of the spiral in gas dynamics based on the continuum data. Results. We find that the pitch angle of a spiral does not differ significantly between gas and dust. The amplitude of the dust spiral decreases with the Stokes number (St) and starts to fade out at a typical St > 0.1 as the dust becomes decoupled from the gas. The semi-analytical model provides an accurate and fast representation of the difference in the surface density of the spiral in dust and gas. We find a spiral in the TW Hya velocity residual map, never seen before, which is a feature in the vertical velocity and has a kink at the continuum gap, yielding strong evidence for a planet at 99 au. Conclusions. We built a model that gives an estimate of the underlying dynamics of dust in a spiral, which can serve as evidence of the planetary origin of spirals and can be a probe for the Stokes number in the disk.

A search for trends in spatially resolved debris discs at far-infrared wavelengths

2020 ◽  
Author(s):  
J P Marshall ◽  
L Wang ◽  
G M Kennedy ◽  
S T Zeegers ◽  
P Scicluna
Keyword(s):  
Scattered Light ◽  
Far Infrared ◽  
Building Blocks ◽  
Young Stars ◽  
Continuum Emission ◽  
Data Set ◽  
Spatially Resolved ◽  
Infrared Wavelengths ◽  
Host Stars ◽  
Protoplanetary Discs

Abstract Debris discs around main sequence stars are belts of planetesimals – asteroids and comets – formed in the protoplanetary discs around young stars. Planetesimals comprise both the building blocks of planets around young stars and the source of dusty debris around older stars. Imaging observations of dust continuum emission and scattered light reveals the location of these planetesimal belts around their host stars. Analysis of debris discs observed at millimetre wavelengths revealed a trend between the discs’ radii and the host star luminosities. This trend was tentatively linked to the preferential formation of dust-producing planetesimals near snow lines (specifically CO) in the protoplanetary discs around the host stars. Here we perform a homogeneous analysis of 96 debris discs observed at far-infrared wavelengths by the Herschel Space Observatory and fit the obtained distribution of radii and widths as a function of stellar luminosity with a power law relation. We identify a trend in disc radius as a function of stellar luminosity similar to that identified at millimetre wavelengths, but cannot convincingly recover it from the available data set due to the large uncertainties on disc radius and width inherent in the marginally spatially resolved data, and the bias of smaller discs around more distant stars (which are also the more luminous) being omitted from our analysis. We see a trend in disc temperature as a function of stellar luminosity, consistent with previous findings from similar analyses.

Exploring the dust ring in the circum-binary disc around GG Tau A

2021 ◽  
Author(s):  
Claudia Toci ◽  
Simone Ceppi ◽  
Nicolas Cuello ◽  
Giuseppe Lodato ◽  
Cristiano Longarini ◽  
...  
Keyword(s):  
Binary Systems ◽  
Planet Formation ◽  
Initial Conditions ◽  
Scattered Light ◽  
Complex Structure ◽  
Semimajor Axis ◽  
Continuum Emission ◽  
Orbital Parameter ◽  
Semi Major Axis ◽  
Multiple Systems

<p>Binaries and multiple systems are common among young stars (Reipurth et al. 2014). These stars are often surrounded by discs of gas and dust, formed due to the conservation of angular momentum of the collapsing cloud, thought to be the site of planet formation.<br />In the case of binary systems, three discs can form: an outer disc surrounding all the stars (called circumbinary disc), and two inner discs around the stars. As circumbinary planets have recently been discovered by Kepler (see e.g., Martin 2018, Bonavita & Desidera 2020), it is crucial to understand the dynamics and evolution of circumbinary discs to better understand the initial conditions of planet formation in multiple systems.<br />The GG Tau A system is an example of a young multiple T Tauri star. The binary is surrounded by a bright disc, observed in the continuum emission at different wavelengths (see e.g., Guilloteau et al. 1999; Dutrey et al. 2014; Phuong et al. 2020b) and in scattered light (e.g., Duchene et al. 2014, Keppler et al. 2020). The disc extends in the dust from 180 to 280 au from the center of mass, and in the gas up to 850 au. The inner (<180 au) part is depleted in gas and dust. Scattered light images show a complex structure in the inner part of the disc, with arcs and filamentary structures connecting the outer ring with the arcs and three shadows.<br />Two different configurations are possible fitting the proper motion data for the system: a co-planar case with a low eccentricity binary with a semi-major axis of 34 au, explored by Cazzoletti et al. 2017 and Keppler et al. 2020, and a misaligned case (i=30) with an eccentric binary (e=0.45) and a wider semimajor axis of 60 au (Aly et al.2018). At the state of the art, all these analyses focused on the gas dynamics only.<br />We will show the results of new 3D SPH simulations of dust and gas performed with the code PHANTOM, devised to test the two possible scenarios. We will describe the dynamics of the system in the two cases, comparing our models with observational results in order to better constraint the orbital parameter of the GG Tau A system. Our predictions will guide future observing campaigns and shed light on the complex evolution of discs in triple stellar systems.</p> <p> </p>

scholarly journals A Multi-Wavelength View of the XMM-Newton Galactic Plane

2014 ◽  
Vol 1 (1) ◽  
pp. 123-126
Author(s):  
Ada Nebot Gómez-Morán ◽  
Christian Motch
Keyword(s):  
Surface Density ◽  
Binary Systems ◽  
Galactic Plane ◽  
Galactic Centre ◽  
Galactic Latitude ◽  
X Ray ◽  
Model Predictions ◽  
Science Centre ◽  
Multi Wavelength ◽  
Galactic Longitude

We present an X-ray survey of the Galactic Plane conducted by the Survey Science Centre of the XMM-Newton satellite. The survey contains more than 1300 X-ray detections at low and intermediate Galactic latitudes and covering 4 deg<sup>2</sup> well spread in Galactic longitude. From a multi-wavelength analysis, using optical spectra and helped by optical and infrared photometry we identify and classify about a fourth of the sources. The observed surface density of soft X-ray (&lt;2 keV) sources decreases with Galactic latitude and although compatible with model predictions at first glance, presents an excess of stars, likely due to giants in binary systems. In the hard band (&gt;2 keV) the surface density of sources presents an excess with respect to the expected extragalactic contribution. This excess highly concentrates towards the direction of the Galactic Centre and is compatible with previous results from Chandra observations around the Galactic Centre. The nature of these sources is still unknown.

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