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Dejan Vinković

Science and Society Synergy Institute
Bana Jospia Jelacica 22B
40000 Cakovec, Croatia
e-mail: dejan_at_iszd.hr
What are the initial conditions for planet formation?
Active Project
Latest update: November 29, 2011
SEE ALSO "Dusty Winds from Young Star"
SEE ALSO "Modeling dust dynamics "

Planets form out of a dense disk of gas and dust around a newborn star. The physical and chemical conditions inside such disks are of crucial importance for planet formation. Nonetheless, these conditions still remain poorly understood. The limiting factor is increasingly on the part of theoretical interpretation of the accumulating wealth of observational data. The difficulty comes from rather complex analysis of transfer of energy within the disk, where the observable energy emerges only after it has experienced a strong reprocessing by the disk's dust.

Sketch of a dusty disk around a star. Images of this disk at various wavelengths and disk inclinations are shown in figures below.
The full theoretical treatment requires rather complex and challenging numerical tasks that can not be performed on a single-processor machines. Therefore, I developed a 2D radiative transfer solver named LELUYA that can go beyond the commonly used simplifications. It provides the full 2D treatment of energy transfer in protoplanetary disks, with high resolution self-adaptive grids. Even more significant step will be possible by merging these calculations with the dust dynamics, which will increase the computational demands even further.

Especially interesting, and still poorly understood, is the environment within several astronomical units (AU = distance between the Earth and the Sun) of these stars. This region comprises the inner protoplanetary disk where dust evolves from submicron particles to terrestrial planets, bipolar jets are launched, disks accrete onto the star and disk winds form.

Dust dynamics in protoplanetary disks brings dust closer to the star than the inner edge of optically thick dusty disk. This extended inner structure is populated only by big grains and it is vertically optically thin. Such conditions enable disk thermal cooling and dust survival.
In the course of my investigation of the inner edge of dusty disks, I discovered that one important radiative transfer solution has been overlooked (Vinkovic 2006, ApJ, 651, 906). The sublimation cutoff of optically thick dusty disks is not a sharp edge, but rather a relatively large zone that extends almost two times closer than the optically thick disk edge. In this zone the disk is vertically thin for the infrared radiation, which allows it to loose excess heat and, therefore, gets closer to the star. In reality, the choice of inner edge properties depends also on the dust dynamics and grain growth. These two processes, together with dust sublimation, shape the inner region of dusty disks. Hence, the evolutionary role of such a large optically thin zone has to be studied further in more detail.

Temperature of dust grains in a disk shown at two spatial scales in cylindrical coordinates for two coexisting grain radii (indicated in images). Rin is the inner disk radius. The dashed line indicates the radial optical depth of tau_V=0.1, while the solid line is tau_V=1. Note how 0.1micron grains survive in the optically thin disc surface only at radial distances larger than 2.2Rin, but in the disc interior they exist very close to Rin. The dotted line shows the vertical optical depth of tau_V=1.

Vinkovic, D. 2012, MNRAS, 420, 1541 (PDF)
Vinkovic, D., & Jurkic, T. 2007, ApJ, 658, 462 (PDF)
Vinkovic, D. 2006, ApJ, 651, 906 (ADS, PDF)
Vinkovic, D., Ivezic, Z., Jurkic, T., & Elitzur, M. 2006, ApJ, 636, 348 (ADS, PDF)



Theoretical disk images are various wavelengths and disk inclination angles.