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Register a new userFirst Images of the Protoplanetary Disk Around PDS 201
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Scattered light imaging has revealed nearly a dozen circumstellar disks around young Herbig Ae/Be stars$-$enabling studies of structures in the upper disk layers as potential signs of on-going planet formation. We present the first images of the disk around the variable Herbig Ae star PDS 201 (V* V351 Ori), and an analysis of the images and spectral energy distribution through 3D Monte-Carlo radiative transfer simulations and forward modelling. The disk is detected in three datasets with LBTI/LMIRCam at the LBT, including direct observations in the $Ks$ and $L$ filters, and an $L$ observation with the 360$^circ$ vector apodizing phase plate coronagraph. The scattered light disk extends to a very large radius of $sim$250 au, which places it among the largest of such disks. Exterior to the disk, we establish detection limits on substellar companions down to $sim$5 M$_{Jup}$ at $gtrsim$1.5 ($gtrsim$500 au), assuming the Baraffe et al. (2015) models. The images show a radial gap extending to $sim$0.4 ($sim$140 au at a distance of 340 pc) that is also evident in the spectral energy distribution. The large gap is a possible signpost of multiple high-mass giant planets at orbital distances ($sim$60-100 au) that are unusually massive and widely-separated compared to those of planet populations previously inferred from protoplanetary disk substructures.
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We present high resolution H-band polarized intensity (PI; FWHM = 0.1: 14 AU) and L-band imaging data (FWHM = 0.11: 15 AU) of the circumstellar disk around the weak-lined T Tauri star PDS 70 in Centaurus at a radial distance of 28 AU (0.2) up to 210 AU (1.5). In both images, a giant inner gap is clearly resolved for the first time, and the radius of the gap is ~70 AU. Our data show that the geometric center of the disk shifts by ~6 AU toward the minor axis. We confirm that the brown dwarf companion candidate to the north of PDS 70 is a background star based on its proper motion. As a result of SED fitting by Monte Carlo radiative transfer modeling, we infer the existence of an optically thick inner disk at a few AU. Combining our observations and modeling, we classify the disk of PDS 70 as a pre-transitional disk. Furthermore, based on the analysis of L-band imaging data, we put an upper limit mass of companions at ~30 to ~50MJ within the gap. Taking account of the presence of the large and sharp gap, we suggest that the gap could be formed by dynamical interactions of sub-stellar companions or multiple unseen giant planets in the gap.
The disk around the Herbig Ae/Be star HD 100546 has been extensively studied and it is one of the systems for which there are observational indications of ongoing and/or recent planet formation. However, up until now no resolved image of the millimeter dust emission or the gas has been published. We present the first resolved images of the disk around HD 100546 obtained in Band 7 with the ALMA observatory. The CO (3-2) image reveals a gas disk that extends out to 350 au radius at the 3-sigma level. Surprisingly, the 870um dust continuum emission is compact (radius <60 au) and asymmetric. The dust emission is well matched by a truncated disk with outer radius of $approx$50 au. The lack of millimeter-sized particles outside the 60 au is consistent with radial drift of particles of this size. The protoplanet candidate, identified in previous high-contrast NACO/VLT L observations, could be related to the sharp outer edge of the millimeter-sized particles. Future higher angular resolution ALMA observations are needed to determine the detailed properties of the millimeter emission and the gas kinematics in the inner region (<2arcsec). Such observations could also reveal the presence of a planet through the detection of circumplanetary disk material.
We report the discovery of a dwarf protoplanetary disk around the star XZ Tau B that shows all the features of a classical transitional disk but on a much smaller scale. The disk has been imaged with the Atacama Large Millimeter/Submillimeter Array (ALMA), revealing that its dust emission has a quite small radius of ~ 3.4 au and presents a central cavity of ~ 1.3 au in radius that we attribute to clearing by a compact system of orbiting (proto)planets. Given the very small radii involved, evolution is expected to be much faster in this disk (observable changes in a few months) than in classical disks (observable changes requiring decades) and easy to monitor with observations in the near future. From our modeling we estimate that the mass of the disk is large enough to form a compact planetary system.
The protoplanetary disk around HL Tau is so far the youngest candidate of planet formation, and it is still embedded in a protostellar envelope with a size of thousands of au. In this work, we study the gas kinematics in the envelope and its possible influence on the embedded disk. We present our new ALMA cycle 3 observational results of HL Tau in the 13CO (2-1) and C18O (2-1) emission at resolutions of 0.8 (110 au), and we compare the observed velocity pattern with models of different kinds of gas motions. Both the 13CO and C18O emission lines show a central compact component with a size of 2 (280 au), which traces the protoplanetary disk. The disk is clearly resolved and shows a Keplerian motion, from which the protostellar mass of HL Tau is estimated to be 1.8+/-0.3 M$_odot$, assuming the inclination angle of the disk to be 47 deg from the plane of the sky. The 13CO emission shows two arc structures with sizes of 1000-2000 au and masses of 3E-3 M$_odot$ connected to the central disk. One is blueshifted and stretches from the northeast to the northwest, and the other is redshifted and stretches from the southwest to the southeast. We find that simple kinematical models of infalling and (counter-)rotating flattened envelopes cannot fully explain the observed velocity patterns in the arc structures. The gas kinematics of the arc structures can be better explained with three-dimensional infalling or outflowing motions. Nevertheless, the observed velocity in the northwestern part of the blueshifted arc structure is ~60-70% higher than the expected free-fall velocity. We discuss two possible origins of the arc structures: (1) infalling flows externally compressed by an expanding shell driven by XZ Tau and (2) outflowing gas clumps caused by gravitational instabilities in the protoplanetary disk around HL Tau.
Theoretical models and spectroscopic observations of newborn stars suggest that protoplantary disks have an inner wall at a distance set by the disk interaction with the star. Around T Tauri stars, the size of this disk hole is expected to be on a 0.1-AU scale that is unresolved by current adaptive optics imaging, though some model-dependent constraints have been obtained by near-infrared interferometry. Here we report the first measurement of the inner disk wall around a solar-mass young stellar object, YLW 16B in the {rho} Ophiuchi star-forming region, by detecting the light travel time of the variable radiation from the stellar surface to the disk. Consistent time lags were detected on two nights, when the time series in H (1.6 {mu}m) and K (2.2 {mu}m) bands were synchronized while the 4.5 {mu}m emission lagged by 74.5 +/- 3.2 seconds. Considering the nearly edge-on geometry of the disk, the inner rim should be 0.084 AU from the protostar on average, with an error of order 0.01 AU. This size is likely larger than the range of magnetospheric truncations, and consistent with an optically and geometrically thick disk front at the dust sublimation radius at ~1500 K. The widths of the cross-correlation functions between the data in different wavebands place possible new constraints on the geometry of the disk.
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