M. Kama

The thermal structure and the location of the snow line in the protosolar nebula: axisymmetric models with full 3-D radiative transfer

The precise location of the water ice condensation front (‘snow line’) in the protosolar nebula has been a debate for a long time. Its importance stems from the expected substantial jump in the abundance of solids beyond the snow line, which is conducive to planet formation, and from the higher ‘stickiness’ in collisions of ice-coated dust grains, which may help the process of coagulation of dust and the formation of planetesimals. In an optically thin nebula, the location of the snow line is easily calculated to be around 3 AU, subject to brightness variations of the young Sun. However, in its first 5–10 myr, the solar nebula was optically thick, implying a smaller snowline radius due to shielding from direct sunlight, but also a larger radius because of viscous heating. Several models have attempted to treat these opposing effects. However, until recently treatments beyond an approximate 1 + 1D radiative transfer were unfeasible. We revisit the problem with a fully self-consistent 3D treatment in an axisymmetric disk model, including a density-dependent treatment of the dust and ice sublimation. We find that the location of the snow line is very sensitive to the opacities of the dust grains and the mass accretion rate of the disk. We show that previous approximate treatments are quite efficient at determining the location of the snow line if the energy budget is locally dominated by viscous accretion. Using this result we derive an analytic estimate of the location of the snow line that compares very well with results from this and previous studies. Using solar abundances of the elements we compute the abundance of dust and ice and find that the expected jump in solid surface density at the snow line is smaller than previously assumed. We further show that in the inner few AU the refractory species are also partly evaporated, leading to a significantly smaller solid state surface density in the regions where the rocky planets were formed.

Volatile-carbon locking and release in protoplanetary disks - A study of TW Hya and HD 100546

The composition of planetary solids and gases is largely rooted in the processing of volatile elements in protoplanetary disks. To shed light on the key processes, we carry out a comparative analysis of the gas-phase carbon abundance in two systems with a similar age and disk mass, but different central stars: HD 100546 and TW Hya. We combine our recent detections of C

Observations and modelling of CO and [C i] in protoplanetary disks - First detections of [C i] and constraints on the carbon abundance

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Determining protoplanetary disk gas masses from CO isotopologues line observations

in these disks with observations of other carbon reservoirs (CO, C

Steepening of the 820 μm continuum surface brightness profile signals dust evolution in TW Hydrae’s disk

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Robustness of N2H+ as tracer of the CO snowline

, C

Near-infrared emission from sublimating dust in collisionally active debris disks

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A dearth of small particles in debris disks - An energy-constrained smallest fragment size

H) and gas mass and warm gas tracers (HD, O

Depletion of chlorine into HCl ice in a protostellar core - The CHESS spectral survey of OMC-2 FIR 4

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Herschel Finds Evidence for Stellar Wind Particles in a Protostellar Envelope: Is This What Happened to the Young Sun?

), as well as spatially resolved ALMA observations and the spectral energy distribution. The disks are modelled with the DALI 2D physical-chemical code. Stellar abundances for HD 100546 are derived from archival spectra. Upper limits on HD emission from HD 100546 place an upper limit on the total disk mass of