On the structure of the transition disk around TW Hydrae

Abstract

Context. For over a decade, the structure of the inner cavity in the transition disk of TW Hydrae has been a subject of debate. Modeling the disk with data obtained at different wavelengths has led to a variety of proposed disk structures. Rather than being inconsistent, the individual models might point to the different faces of physical processes going on in disks, such as dust growth and planet formation. Aims. Our aim is to investigate the structure of the transition disk again and to find to what extent we can reconcile apparent model differences. Methods. A large set of high-angular-resolution data was collected from near-infrared to centimeter wavelengths. We investigated the existing disk models and established a new self-consistent radiative-transfer model. A genetic fitting algorithm was used to automatize the parameter fitting, and uncertainties were investigated in a Bayesian framework. Results. Simple disk models with a vertical inner rim and a radially homogeneous dust composition from small to large grains cannot reproduce the combined data set. Two modifications are applied to this simple disk model: (1) the inner rim is smoothed by exponentially decreasing the surface density in the inner ∼3 AU, and (2) the largest grains (>100 µm) are concentrated towards the inner disk region. Both properties can be linked to fundamental processes that determine the evolution of protoplanetary disks: the shaping by a possible companion and the different regimes of dust-grain growth, respectively. Conclusions. The full interferometric data set from near-infrared to centimeter wavelengths requires a revision of existing models for the TW Hya disk. We present a new model that incorporates the characteristic structures of previous models but deviates in two key aspects: it does not have a sharp edge at 4 AU, and the surface density of large grains differs from that of smaller grains. This is the first successful radiative-transfer-based model for a full set of interferometric data.

Discovery of a Disk Gap Candidate at 20 Au in Tw Hydrae

“…Estimates of the amount of 10 μm-1 mm sized dust in the disk midplane and up to ∼60 AU are limited by SMA and VLA data (see Figure 9 of Menu et al 2014). Our NIR observations trace dust at the disk surface between 10 and 80 AU, and reflect mainly smaller grains 0.1-10 μm in size.…”

An ALMA Survey of DCN/H13CN and DCO+/H13CO+ in Protoplanetary Disks

“…An alternative scenario is that radial drift in the LkCa 15 disk creates a radial thermal inversion allowing for the warm CH 2 D + pathway to produce DCN just outside the millimeter dust disk (Cleeves 2016). Then, other disks exhibiting evidence of radial drift, such as TW Hya and AS 209 (Menu et al 2014;Pérez et al 2012), might be expected to show similar DCN emission, but they do not at the current sensitivity.…”

A photoevaporative gap in the closest planet-forming disc

“…More recently Menu et al (2014) presented a new model, which was able to fit all interferometric observations from near-infrared to cm wavelengths available at the time. This model required an inner cavity with radius 0.3 − 0.5 au with a maximum in the surface density occurring at ∼ 2.5 au.…”