Annular structures in proto-planetary discs, such as gaps and rings, are now ubiquitously found by high-resolution ALMA observations. Under the hypothesis that they are opened by planets, in this... Show moreAnnular structures in proto-planetary discs, such as gaps and rings, are now ubiquitously found by high-resolution ALMA observations. Under the hypothesis that they are opened by planets, in this paper we investigate how the minimum planet mass needed to open a gap varies across different stellar host masses and distances from the star. The dependence on the stellar host mass is particularly interesting because, at least in principle, gap opening around low mass stars should be possible for lower mass planets, giving us a look into the young, low mass planet population. Using dusty hydrodynamical simulations, we find however the opposite behaviour, as a result of the fact that discs around low mass stars are geometrically thicker: gap opening around low mass stars can require more massive planets. Depending on the theoretical isochrone employed to predict the relationship between stellar mass and luminosity, the gap opening planet mass could also be independent of stellar mass, but in no case we find that gap opening becomes easier around low mass stars. This would lead to the expectation of a lower incidence of such structures in lower mass stars, since exoplanet surveys show that low mass stars have a lower fraction of giant planets. More generally, our study enables future imaging observations as a function of stellar mass to be interpreted using information on the mass vs. luminosity relations of the observed samples. Show less
Keppler, M.; Teague, R.; Bae, J.; Benisty, M.; Henning, T.; Boekel, R. van; ... ; Semenov, D. 2019
The Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the... Show moreThe Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the case that a breakthrough in angular resolution imaging capabilities is required in order to unravel the processes involved in planet formation. PFI will be optimised to provide a complete census of the protoplanet population at all stellocentric radii and over the age range from 0.1 to 100 Myr. Within this age period, planetary systems undergo dramatic changes and the final architecture of planetary systems is determined. Our goal is to study the planetary birth on the natural spatial scale where the material is assembled, which is the "Hill Sphere" of the forming planet, and to characterise the protoplanetary cores by measuring their masses and physical properties. Our science working group has investigated the observational characteristics of these young protoplanets as well as the migration mechanisms that might alter the system architecture. We simulated the imprints that the planets leave in the disk and study how PFI could revolutionise areas ranging from exoplanet to extragalactic science. In this contribution we outline the key science drivers of PFI and discuss the requirements that will guide the technology choices, the site selection, and potential science/technology tradeoffs. Show less
Boer, J. de; Salter, G.; Benisty, M.; Vigan, A.; Boccaletti, A.; Pinilla, Ortiz P.A.; ... ; Zurlo, A. 2016
Context. The protoplanetary disk around the F-type star HD 135344B (SAO 206462) is in a transition stage and shows many intriguing structures both in scattered light and thermal (sub-... Show moreContext. The protoplanetary disk around the F-type star HD 135344B (SAO 206462) is in a transition stage and shows many intriguing structures both in scattered light and thermal (sub-)millimeter emission which are possibly related to planet formation processes. Aims. We aim to study the morphology and surface brightness of the disk in scattered light to gain insight into the innermost disk regions, the formation of protoplanets, planet-disk interactions traced in the surface and midplane layers, and the dust grain properties of the disk surface. Methods. We have carried out high-contrast polarimetric differential imaging (PDI) observations with VLT/SPHERE and obtained polarized scattered light images with ZIMPOL in the R and I-bands and with IRDIS in the Y and J-bands. The scattered light images and surface brightness profiles are used to study in detail structures in the disk surface and brightness variations. We have constructed a 3D radiative transfer model to support the interpretation of several detected shadow features. Results. The scattered light images reveal with unprecedented angular resolution and sensitivity the spiral arms as well as the 25 au cavity of the disk. Multiple shadow features are discovered on the outer disk with one shadow only being present during the second observation epoch. A positive surface brightness gradient is observed in the stellar irradiation corrected (r2-scaled) images in southwest direction possibly due to an azimuthally asymmetric perturbation of the temperature and/or surface density by the passing spiral arms. The disk integrated polarized flux, normalized to the stellar flux, shows a positive trend towards longer wavelengths which we attribute to large (2πa λ) aggregate dust grains in the disk surface. Part of the non-azimuthal polarization signal in the Uφ image of the J-band observation can be attributed to multiple scattering in the disk. Conclusions. The detected shadow features and their possible variability have the potential to provide insight into the structure of and processes occurring in the innermost disk regions. Possible explanations for the presence of the shadows include a 22◦ misaligned inner disk, a warped disk region that connects the inner disk with the outer disk, and variable or transient phenomena such as a perturbation of the inner disk or an asymmetric accretion flow. The spiral arms are best explained by one or multiple protoplanets in the exterior of the disk although no gap is detected beyond the spiral arms up to 1."0. Show less
Benisty, M.; Juhasz, A.; Boccaletti, A.; Avenhaus, H.; Milli, J.; Thalmann, C.; ... ; Pueyo, L. 2015
Disk winds have been postulated as a mechanism for angular momentum release in protostellar systems for decades. HD 163296 is a Herbig Ae star surrounded by a disk and has been shown to host a... Show moreDisk winds have been postulated as a mechanism for angular momentum release in protostellar systems for decades. HD 163296 is a Herbig Ae star surrounded by a disk and has been shown to host a series of HH knots (HH 409) with bow shocks associated with the farthest knots. Here we present ALMA science verification data of CO J = 2-1 and J = 3-2 emission, which are spatially coincident with the blue shifted jet of HH knots, and offset from the disk by -18.6 km s$^{-1}$. The emission has a double corkscrew morphology and extends more than 10'' from the disk with embedded emission clumps coincident with jet knots. We interpret this double corkscrew as emission from material in a molecular disk wind, and that the compact emission near the jet knots is being heated by the jet that is moving at much higher velocities. We show that the J = 3-2 emission is likely heavily filtered by the interferometer, but the J = 2-1 emission suffers less due to the larger beam and sensitivity to larger scale structures. Excitation analysis suggests temperatures exceeding 900 K in these compact features, with the wind mass, momentum and energy being of order 10$^{-5}$ M$_{⊙}$, 10$^{-4}$ M$_{⊙}$ km s$^{-1}$ and 10$^{40}$ erg, respectively. The high mass loss rate suggests that this star is dispersing the disk faster than it is funneling mass onto the star. Show less
Gregorio-Monsalvo, I.; Ménard, F.; Dent, W.; Pinte, C.; López, C.; Klaassen, P.D.; ... ; Van Kempen, T. 2013
Aims: The aim of this work is to study the structure of the protoplanetary disk surrounding the Herbig Ae star HD 163296. Methods: We used high-resolution and high-sensitivity ALMA observations... Show moreAims: The aim of this work is to study the structure of the protoplanetary disk surrounding the Herbig Ae star HD 163296. Methods: We used high-resolution and high-sensitivity ALMA observations of the CO(3-2) emission line and the continuum at 850 {$μ$}m, as well as the three-dimensional Monte Carlo radiative transfer code, MCFOST, to model the data presented in this work. Results: The CO(3-2) emission unveils for the first time at submillimeter frequencies the vertical structure details of a gaseous disk in Keplerian rotation, showing the back and front sides of a flared disk. Continuum emission at 850 {$μ$}m reveals a compact dust disk with a 240 AU outer radius and a surface brightness profile that shows a very steep decline at radius larger than 125 AU. The gaseous disk is more than two times larger than the dust disk, with a similar critical radius but with a shallower radial profile. Radiative transfer models of the continuum data confirm the need for a sharp outer edge to the dust disk. The models for the CO(3-2) channel map require the disk to be slightly more geometrically thick than previous models suggested, and that the temperature at which CO gas becomes depleted (i.e., frozen out) from the outer regions of the disk midplane is T {lt} 20 K, in agreement with previous studies. Show less
