THE MISSING CAVITIES IN THE SEEDS POLARIZED SCATTERED LIGHT IMAGES OF TRANSITIONAL PROTOPLANETARY DISKS: A GENERIC DISK MODEL

Aims. We aim to study vertical settling and radial drift of dust in protoplanetary disks from a different perspective: an edge-on view. An estimation of the amplitude of settling and drift is highly relevant to understanding planet formation. Methods. We analyze a sample of 12 HST-selected edge-on protoplanetary disks (i.e., seen with high inclinations) for which the vertical extent of the emission layers can be constrained directly. We present ALMA high angular resolution continuum images (~0.1′′) of these disks at two wavelengths, 0.89 and 2.06 mm (respectively ALMA bands 7 and 4), supplemented with archival band 6 data (1.33 mm) where available. Results. Several sources show constant brightness profiles along their major axis with a steep drop at the outer edges. Two disks have central holes with additional compact continuum emission at the location of the central star. For most sources, the millimeter continuum emission is more compact than the scattered light, both in the vertical and radial directions. Six sources are resolved along their minor axis in at least one millimetric band, providing direct information on the vertical distribution of the millimeter grains. For the second largest disk of the sample, Tau 042021, the significant difference in vertical extent between band 7 and band 4 suggests efficient size-selective vertical settling of large grains. Furthermore, the only Class I object in our sample shows evidence of flaring in the millimeter. Along the major axis, all disks are well resolved. Four of them are larger in band 7 than in band 4 in the radial direction, and three have a similar radial extent in all bands. These three disks are also the ones with the sharpest apparent edges (between 80% and 20% of the peak flux, Δr∕r ~ 0.3), and two of them are binaries. For all disks, we also derive the millimeter brightness temperature and spectral index maps. We find that all edge-on disks in our sample are likely optically thick and that the dust emission reveals low brightness temperatures in most cases (brightness temperatures ≤10 K). The integrated spectral indices are similar to those of disks at lower inclination. Conclusions. The comparison of a generic radiative transfer disk model with our data shows that at least three disks are consistent with a small millimeter dust scale height, of a few au (measured at r = 100 au). This is in contrast with the more classical value of hg ~ 10 au derived from scattered light images and from gas line measurements. These results confirm, by direct observations, that large (millimeter) grains are subject to significant vertical settling in protoplanetary disks.

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Shadowing and multiple rings in the protoplanetary disk of HD 139614

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936509 ◽

2020 ◽

Vol 635 ◽

pp. A121 ◽

Cited By ~ 3

Author(s):

G. A. Muro-Arena ◽

M. Benisty ◽

C. Ginski ◽

C. Dominik ◽

S. Facchini ◽

...

Keyword(s):

Radiative Transfer ◽

Scattered Light ◽

Protoplanetary Disks ◽

Position Angle ◽

Protoplanetary Disk ◽

Disk Model ◽

Outer Disk ◽

Planetary Mass ◽

Azimuthal Asymmetries ◽

Multiple Rings

Context. Shadows in scattered light images of protoplanetary disks are a common feature and support the presence of warps or misalignments between disk regions. These warps are possibly caused by an inclined (sub-)stellar companion embedded in the disk. Aims. We aim to study the morphology of the protoplanetary disk around the Herbig Ae star HD 139614 based on the first scattered light observations of this disk, which we model with the radiative transfer code MCMax3D. Methods. We obtained J- and H-band observations that show strong azimuthal asymmetries in polarized scattered light with VLT/SPHERE. In the outer disk, beyond ~30 au, a broad shadow spans a range of ~240 deg in position angle, in the east. A bright ring at ~16 au also shows an azimuthally asymmetric brightness, with the faintest side roughly coincidental with the brightest region of the outer disk. Additionally, two arcs are detected at ~34 and ~50 au. We created a simple four-zone approximation to a warped disk model of HD 139614 in order to qualitatively reproduce these features. The location and misalignment of the disk components were constrained from the shape and location of the shadows they cast. Results. We find that the shadow on the outer disk covers a range of position angles too wide to be explained by a single inner misaligned component. Our model requires a minimum of two separate misaligned zones – or a continuously warped region – to cast this broad shadow on the outer disk. A small misalignment of ~4° between adjacent components can reproduce most of the observed shadow features. Conclusions. Multiple misaligned disk zones, potentially mimicking a warp, can explain the observed broad shadows in the HD 139614 disk. A planetary mass companion in the disk, located on an inclined orbit, could be responsible for such a feature and for the dust-depleted gap responsible for a dip in the SED.

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Searching for H2 emission from protoplanetary disks using near- and mid-infrared high-resolution spectroscopy

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308016827 ◽

2007 ◽

Vol 3 (S249) ◽

pp. 359-368

Author(s):

A. Carmona ◽

M. E. van den Ancker ◽

Th. Henning ◽

Ya. Pavlyuchenkov ◽

C. P. Dullemond ◽

...

Keyword(s):

Surface Layer ◽

High Resolution ◽

Near Infrared ◽

Protoplanetary Disks ◽

High Resolution Spectroscopy ◽

Disk Model ◽

Mid Infrared ◽

T Tauri ◽

Hα Emission ◽

Ir Emission

AbstractThe mass and dynamics of protoplanetary disks are dominated by molecular hydrogen (H2). However, observationally very little is known about the H2. In this paper, we discuss two projects aimed to constrain the properties of H2 in the disk's planet forming region (R<50AU). First, we present a sensitive survey for pure-rotational H2 emission at 12.278 and 17.035 μm in a sample of nearby Herbig Ae/Be and T Tauri stars using VISIR, ESO's VLT high-resolution mid-infrared spectrograph. Second, we report on a search for H2 ro-vibrational emission at 2.1228, 2.2233 and 2.2477 μm in the classical T Tauri star LkHα 264 and the debris disk 49 Cet employing CRIRES, ESO's VLT high-resolution near-infrared spectrograph.VISIR project: none of the sources show H2 mid-IR emission. The observed disks contain less than a few tenths of MJupiter of optically thin H2 at 150 K, and less than a few MEarth at T>300 K. % and higher T. Our non-detections are consistent with the low flux levels expected from the small amount of H2 gas in the surface layer of a Chiang and Goldreich (1997) Herbig Ae two-layer disk model. In our sources the H2 and dust in the surface layer have not significantly departed from thermal coupling (Tgas/Tdust<2) and the gas-to-dust ratio in the surface layer is very likely <1000.CRIRES project: The H2 lines at 2.1218 μm and 2.2233 μm are detected in LkHα 264. An upper limit on the 2.2477 μm H2 line flux in LkHα 264 is derived. 49 Cet does not exhibit H2 emission in any of observed lines. There are a few MMoon of optically thin hot H2 in the inner disk (∼0.1 AU) of LkHα 264, and less than a tenth of a MMoon of hot H2 in the inner disk of 49 Cet. The shape of the 1–0 S(0) line indicates that LkHα disk is close to face-on (i<35o). The measured 1–0 S(0)/1–0 S(1) and 2–1 S(1)/1–0 S(1) line ratios in LkHα 264 indicate that the H2 is thermally excited at T<1500 K. The lack of H2 emission in the NIR spectra of 49 Cet and the absence of Hα emission suggest that the gas in the inner disk of 49 Cet has dissipated.

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Dust-driven viscous ring-instability in protoplanetary disks

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731878 ◽

2018 ◽

Vol 609 ◽

pp. A50 ◽

Cited By ~ 24

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.

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Shadows and asymmetries in the T Tauri disk HD 143006: evidence for a misaligned inner disk

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833913 ◽

2018 ◽

Vol 619 ◽

pp. A171 ◽

Cited By ~ 31

Author(s):

M. Benisty ◽

A. Juhász ◽

S. Facchini ◽

P. Pinilla ◽

J. de Boer ◽

...

Keyword(s):

Large Scale ◽

Near Infrared ◽

Scattered Light ◽

Three Dimensional ◽

Angular Separation ◽

Position Angle ◽

Disk Model ◽

Disk Structure ◽

T Tauri ◽

Western Side

Context. While planet formation is thought to occur early in the history of a protoplanetary disk, the presence of planets embedded in disks, or of other processes driving disk evolution, might be traced from their imprints on the disk structure. Aims. We study the morphology of the disk around the T Tauri star HD 143006, located in the ~5–11 Myr-old Upper Sco region, and we look for signatures of the mechanisms driving its evolution. Methods. We observed HD 143006 in polarized scattered light with VLT/SPHERE at near-infrared (J-band, 1.2 μm) wavelengths, reaching an angular resolution of ~0.037′′ (~6 au). We obtained two datasets, one with a 145 mas diameter coronagraph, and the other without, enabling us to probe the disk structure down to an angular separation of ~0.06′′ (~10 au). Results. In our observations, the disk of HD 143006 is clearly resolved up to ~0.5′′ and shows a clear large-scale asymmetry with the eastern side brighter than the western side. We detect a number of additional features, including two gaps and a ring. The ring shows an overbrightness at a position angle (PA) of ~140°, extending over a range in position angle of ~60°, and two narrow dark regions. The two narrow dark lanes and the overall large-scale asymmetry are indicative of shadowing effects, likely due to a misaligned inner disk. We demonstrate the remarkable resemblance between the scattered light image of HD 143006 and a model prediction of a warped disk due to an inclined binary companion. The warped disk model, based on the hydrodynamic simulations combined with three-dimensional radiative transfer calculations, reproduces all major morphological features. However, it does not account for the observed overbrightness at PA ~ 140°. Conclusions. Shadows have been detected in several protoplanetary disks, suggesting that misalignment in disks is not uncommon. However, the origin of the misalignment is not clear. As-yet-undetected stellar or massive planetary companions could be responsible for them, and naturally account for the presence of depleted inner cavities.

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Evolution of protoplanetary disks from their taxonomy in scattered light: Group I vs. Group II

Astronomy and Astrophysics ◽

10.1051/0004-6361/201630320 ◽

2017 ◽

Vol 603 ◽

pp. A21 ◽

Cited By ~ 28

Author(s):

A. Garufi ◽

G. Meeus ◽

M. Benisty ◽

S. P. Quanz ◽

A. Banzatti ◽

...

Keyword(s):

Scattered Light ◽

Protoplanetary Disks ◽

Group I ◽

Group Ii ◽

Light Group

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New mid-infrared imaging constraints on companions and protoplanetary disks around six young stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/202039261 ◽

2021 ◽

Vol 648 ◽

pp. A92

Author(s):

D. J. M. Petit dit de la Roche ◽

N. Oberg ◽

M. E. van den Ancker ◽

I. Kamp ◽

R. van Boekel ◽

...

Keyword(s):

Spectral Energy Distribution ◽

Protoplanetary Disks ◽

Occurrence Rate ◽

Spectral Energy ◽

Disk Model ◽

Mid Infrared ◽

Geometrical Properties ◽

Planetary Mass ◽

Upper Limits ◽

Ir Emission

Context. Mid-infrared (mid-IR) imaging traces the sub-micron and micron-sized dust grains in protoplanetary disks and it offers constraints on the geometrical properties of the disks and potential companions, particularly if those companions have circumplanetary disks. Aims. We use the VISIR instrument and its upgrade NEAR on the VLT to take new mid-IR images of five (pre-)transition disks and one circumstellar disk with proposed planets and obtain the deepest resolved mid-IR observations to date in order to put new constraints on the sizes of the emitting regions of the disks and the presence of possible companions. Methods. We derotated and stacked the data to find the disk properties. Where available, we compare the data to PRODIMO (Protoplanetary Disk Model) radiation thermo-chemical models to achieve a deeper understanding of the underlying physical processes within the disks. We applied the circularised point spread function subtraction method to find upper limits on the fluxes of possible companions and model companions with circumplanetary disks. Results. We resolved three of the six disks and calculated position angles, inclinations, and (upper limits to) sizes of emission regions in the disks, improving upper limits on two of the unresolved disks. In all cases the majority of the mid-IR emission comes from small inner disks or the hot inner rims of outer disks. We refined the existing PRODIMO HD 100546 model spectral energy distribution (SED) fit in the mid-IR by increasing the PAH abundance relative to the ISM, adopting coronene as the representative PAH, and increasing the outer cavity radius to 22.3 AU. We produced flux estimates for putative planetary-mass companions and circumplanetary disks, ruling out the presence of planetary-mass companions with L > 0.0028 L⊙ for a > 180 AU in the HD 100546 system. Upper limits of 0.5–30 mJy are obtained at 8–12 μm for potential companions in the different disks. We rule out companions with L > 10−2 L⊙ for a > 60 AU in TW Hydra, a > 110 AU in HD 169142, a > 150 AU in HD 163296, and a > 160 AU in HD 36112. Conclusions. The mid-IR emission comes from the central regions and traces the inner areas of the disks, including inner disks and inner rims of outer disks. Planets with mid-IR luminosities corresponding to a runaway accretion phase can be excluded from the HD 100546, HD 169142, TW Hydra, and HD 36112 systems at separations >1′′. We calculated an upper limit to the occurrence rate of wide-orbit massive planets with circumplanetary disks of 6.2% (68% confidence). Future observations with METIS on the ELT will be able to achieve a factor of 10 better sensitivity with a factor of five better spatial resolution. MIRI on JWST will be able to achieve 250 times better sensitivity. Both will possibly detect the known companions to all six targets.

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