chemistry in protoplanetary disks

My research highlight today was a great talk by Ilse Cleeves (Harvard) about ALMA observations of the dust and molecular gas in proto-planetary disks. She showed that you can see chemical gradients in the disks, including rings and lines of formation of molecules. Much of what's visible is on the outer surfaces of the disk, which is illuminated by the young, accreting star, because the interior parts of the disk are optically thick. Because the chemical models are heavy and imperfect, I proposed looking at latent-variable models to describe the observed molecular abundances; maybe there are interesting features to be found even without relying on physical or chemical models?

The most remarkable thing she showed is time-domain chemical results: She can see chemical changes in real time as the disk responds to (presumably) stellar flares on day-ish time-scales! We discussed methods for distinguishing different kinds of events that might be triggering the chemical changes. Expect denser time sampling in the future; it's ALMA proposal-writing season!

Technically, my favorite part of Cleeves's work is that she does all of her model-fitting and hypothesis comparing in the visibilities. That is, she doesn't make an image from the interferometric data and then model it: She takes her models to the Fourier domain and compares to the raw data. That's classy.

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