Monte-Carlo radiative transfer simulation of the circumstellar disk of the Herbig Ae star HD 144432

Abstract

Context. Studies of pre-transitional disks, with a gap region between the inner near-infrared-emitting region and the outer disk, are important to improving our understanding of disk evolution and planet formation. Previous infrared interferometric observations have shown hints of a gap region in the protoplanetary disk around the Herbig Ae star HD 144432. Aims. We study the dust distribution around this star with two-dimensional radiative transfer modeling. Methods. We compare the model predictions obtained via the Monte-Carlo radiative transfer code RADMC-3D with infrared interferometric observations and the spectral energy distribution of HD 144432. Results. The best-fit model that we found consists of an inner optically thin component at 0.21-0.32 AU and an optically thick outer disk at 1.4-10 AU. We also found an alternative model in which the inner sub-AU region consists of an optically thin and an optically thick component. Conclusions. Our modeling suggests an optically thin component exists in the inner sub-AU region, although an optically thick component may coexist in the same region. Our modeling also suggests a gap-like discontinuity in the disk of HD 144432.

A study of dust properties in the inner sub-au region of the Herbig Ae star HD 169142 with VLTI/PIONIER

“…Due to the much larger opacity of the small grains, the optical-NIR opacity is dominated by the small graphite grain and the silicate is introduced purely for interpreting the N-band silicate feature. For HD 144432 (Chen et al 2016), a even narrower gap between ∼0.3 au and ∼1.4 au was found, and the NIR emitting material is likely optically thin dust consisting of mainly sub-micron grains.…”

“…The color of the overall emission is determined by complicated radiative transfer processes involving both the surface layers and the interior. Numerical studies of the radiative transfer processes show that the overall color is insensitive to ǫ (see e.g., Dullemond & Monnier 2010;Chen et al 2016).…”

Mid-infrared evidence for iron-rich dust in the multi-ringed inner disk of HD 144432

“…In reality, the rings may have a rounded radial profile, but it is out of the scope of this study to constrain that aspect. Chen et al (2016a) performed radiative transfer simulations to fit a set of H, K, and N band interferometric data on HD 144432. Their best model (coined DA0) features an inner disk between 0.2 and 0.3 au, which is optically thin at λ = 2 µm in the midplane in the radial direction; and an optically thick outer disk between 1.4 and 10 au.…”

“…As in our modeling we do not represent the vertical extent of the disk, we cannot address this question. Chen et al (2016a) explored this aspect in their RADMC-3D simulations with a puffed-up inner rim as the source of shadowing. They found that the self-shadowed model does not fit the data well, as it provides too low flux in the near-IR, and too much flux at 10-100 µm.…”

“…They also needed a spatially extended halo component to fit their data. In their subsequent paper (Chen et al 2016a), they presented radiative transfer simulations with RADMC-3D using H (IOTA, AMBER), K (Keck Interferometer, AMBER), and N band (MIDI) data. Their best-fit model features an optically thin inner disk component between 0.2 and 0.3 au, and an optically thick outer disk between 1.4 and 10 au.…”