H2O emission as tracer of pebble drift: Insights from coupling transport and thermochemical models
Year: 2026
Type: article
Abstract: The composition of the inner regions of protoplanetary disks is known to change over time due to the delivery of icy grains. Cold emission is often hypothesized to be a tracer of this pebble drift, as sublimating ices might get mixed vertically upward into the surface layers of the disk, where this cold gas can potentially be observed with JWST. However, it is unclear the extent to which processes such as photodissociation or the co-delivery of dust, which would obscure the delivered , would impede such detections. H2O H2O H2O The transport of gas and dust through a disk is often considered using 1D models, whereas more complex 2D models that include a full chemical network are often static in nature. We aim to combine the two modeling approaches to obtain an improved, 2D view of transport in disks. This would allow us to better understand how to trace these processes; for example, via emission, as seen with JWST-MIRI. H2O We combined the 1D transport code DiscEvolution with the 2D thermochemical code DALI to create several grids of models in which the gas-phase abundances or dust properties (or both) were varied according to the transport model. Several snapshots from a DiscEvolution were taken and postprocessed in DALI, considering times from 10^4 to 4 snow line, allowing dust to pile up there, as well as one scenario without the presence of a traffic jam. yr. The delivered abundances were instantaneously mixed up vertically and the chemistry was run for 10^3 yr. We considered one scenario with a traffic jam present inside the H2O The transport of both gas and dust leads to significant temperature changes within the disk, which strongly influence line fluxes and ratios. When a traffic jam is present, the delivery of can indeed proceed unnoticed due to the co-delivery of dust, as the retrieved mass from LTE slab fits does not change. In addition, the relative strength of cold lines is not found to be sensitive to this delivery of gas-phase : it would need to rapidly diffuse outward and upward in the disk after sublimation to be observed as such with JWST-MIRI. Instead, the cold lines can be greatly enhanced by the delivery of only dust to the inner disk when a traffic jam is present, due to the preferential obscuration of the warm and hot reservoirs by this dust pile-up. Therefore, it is possible to create a spectrum with strong cold emission (a signature hypothesized to trace the delivery of ices across the snow line) solely through the delivery of dust, rather than . We briefly discuss the case of / as a tracer as well, but without any clear trend reported. H2O H2O H2O H2O H2O H2O H2O H2O H2O CO2 H2O Recent works have used the 1500/6000 K line ratio as a proxy to determine the pebble mass flux crossing the snow line; however, we find that the use of this line ratio for this purpose warrants some caution. The line ratio is rather sensitive to the temperature and dust distribution of the disk. It is often influenced not only by the cold mass, but also by the hot mass. Both of these properties can fluctuate considerably during the evolution of the disk. This might then introduce complexities and trends as a function of time that do not match the true evolution of the pebble flux over time. H2O H2O H2O H2O
Source: Astronomy and Astrophysics
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W7213390861