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Astrophysics Colloquium

Chemical Structure and Finding Proto-Planets in the Age of ALMA
Presented by Ted Bergin
University of Michigan

Thursday, April 25, 2019
11:00 A.M. in 169-336

Abstract
The Atacama Large Millimeter Array has been in operation for several years and has revealed significant physical and chemical structure within planet-forming disks. In this talk, I will discuss how to link the chemical structure to the expanding field of exoplanetary atmospheric characterization. In planetary atmospheres, equilibrium chemistry will redistribute elements into specific carriers depending on local conditions. Therefore to draw a link between planet formation and end-state composition, we need to measure absolute abundances and trace the bulk carriers of key elements. In this talk, I will discuss methods to determine bulk abundances, relative to hydrogen, within protoplanetary disks to provide grounding data on the disposition of elemental C during the phase of giant planet formation. The understanding of chemical structure also unlocks our ability to use molecular emission to trace the presence of hidden exoplanets. I will present a new technique that relies on measuring velocity residuals in the emission of CO isotopologues that deviate from Keplerian rotation with 2 m/s accuracy. In the HD 163296 disk, these residuals directly trace gradients in the hydrogen gas pressure across the gaps, without need for a priori knowledge of absolute scaling factors. This unique method provides the strongest evidence to data that gaps in dust and gas emission are true gaps in the H2 distribution, hinting at the presence of unseen Jupiter mass planets in these Myr-old systems.

JPL Contact: Paul Goldsmith (3-0518)


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