With just under 12 hours to go, here's how JWST Cycle 5 proposal submissions are progressing according to our sampling of the star and planet formation people here in Leiden! We're well past the 1000 mark for the year (and 10,000 across all years!) now, but where will we end up?

However the strong CO2 is particularly exciting, because we see not only CO2 itself but potentially two of its isotopologues - 13CO2 and CO18O (more tenatively) - where one of the atoms has been replaced by a rarer isotope. The shapes and relative strengths of the emission features imply that... 3/4

Marissa found that CX Tau is an example of the discs with weak water but strong CO2. The weakness of the water is more or less in line with what one expects for given the disc's low accretion rate, though there is still evidence for cold water strong emission which may be connected to drift. 2/4

The latest protoplanetary disk study by the MINDS collaboration using JWST-MIRI is out now! arxiv.org/abs/2412.127... Led by Leiden PhD student Marissa Vlasblom, it focusses on CX Tau, a disk for which the dust emission is much more compact than gas, suggesting dust grains have drifted inwards. 1/4

However, the dust emits too: the 2 disc spectra that I showed for reference had had the dust emission (which is a smooth underlying variation) subtracted. This is the raw spectrum of GW Lup from Grant et al. 2023, where you can see the same line features atop the larger scale continuum variations.

Thankfully, the dust does not alter the ratio of CO2/H2O that could be seen, which always closely follows the true mass ratio. So comparing the two molecules could be the best way to test when radial drift is playing a role in inner disc compositions and at what stage of evolution the disc is. 6/6

But what can we actually see with JWST? It becomes a little complicated because the drift naturally supplies dust which might help to obscure some of the molecules we seek to observe! In the worst case scenario (labelled Scenario 1 in the figure) we would see no enhancement in the water at all! 5/6

The delivery of CO2 happens slightly later and lasts longer: it is more volatile than H2O so sublimates further out in the disc and so takes longer to accrete onto the star. If radial drift is interrupted, e.g. by dust traps, H2O disappears more quickly and the disc becomes relatively CO2-rich. 3/6

Dust grains in discs undergo an inward migration process known as radial drift .This has been argued to lead to enhancements of H2O as the dust grains are coated in ice which they release when they reach the warm inner disc. The dust will also carry CO2 ice, and should therefore enhance CO2 too. 2/6

It's paper day! arxiv.org/abs/2412.01895 JWST is studying the molecular contents of the inner regions of protoplanetary discs in unprecented detail, and they turn out to be very varied. Some discs, eg DR Tau, are dominated by emission from water, others, eg GW Lup, are dominated by CO2. But why? 1/6