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Astrophysics Luncheon Seminar

Tracing Chemical Inheritance in Protoplanetary Disks
Presented by Ryan Loomis
National Radio Astronomy Observatory

Monday, April 29, 2019
12:00 noon in 169-336

Abstract
The chemical composition of nascent planets is set by the molecular inventories of the dust and gas rich protoplanetary disks in which they form. Understanding these environments is therefore crucial to predicting potential habitability, as well as uncovering the origin of Earth's organic reservoir. Recent gains in the sensitivity and resolution of (sub)mm observations have revolutionized our understanding of disk chemistry, enabling the detection of prebiotic precursors such as CH3CN, CH3OH, and HCOOH. Major challenges remain, however, including how to connect ALMA observations of gas-phase disk organics with the bulk icy reservoir responsible for comet and planet formation. Such extrapolations require both (1) complete disk molecular inventories and (2) detailed characterization of molecular abundance distributions. In this talk I discuss recent observational progress toward these two goals, enabling better constraint of disk chemical models and comparisons to Solar System cometary measurements.

First, I present a new analysis technique for detecting weak spectral lines and highlight results from its application to an unbiased ALMA spectral line survey of two disks. Five new molecular species are detected for the first time in disks, a ~20% increase in the the number of known disk species. Second, I present new observations of the complex organics CH3CN and CH3OH toward a small sample of disks and interpret these results in the context of protostellar inheritance vs. disk chemical reset. Comparing chemical model predictions of CH3CN abundances with Solar System cometary measurements, I show that inheritance of nitriles from interstellar ices likely occurred in the Solar Nebula, in agreement with recent results from the Rosetta mission.

JPL Contact: Liton Majumdar


SVCP Astrophysics


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