Jessica Speedie

Topic

Planet Hunting and the Dynamical Structure of Planet-forming Disks

Department of Physics and Astronomy

Date & location

• Friday, July 25, 2025
• 8:00 A.M.
• Clearihue Building, Room B019

Examining Committee

Supervisory Committee

• Dr. Ruobing Dong, Department of Physics and Astronomy, University of Victoria (Supervisor)
• Dr. Doug Johnstone, Department of Physics and Astronomy, UVic (Member)
• Dr. JJ Kavelaars, Department of Physics and Astronomy, UVic (Member)
• Dr. Ryan Loomis, Assistant Scientist, National Radio Astronomy Observatory (Outside Member)

External Examiner

• Dr. Cornelis Dullemond, Center for Astronomy, Heidelberg University

Chair of Oral Examination

• Dr. Don Juzwishin, School of Health Information Science, UVic

Abstract

The assembly of planetary systems unfolds within the reservoir of ‘leftover’ material surrounding newborn stars. This thesis explores the use of interferometric observations at millimeter wavelengths to provide clues for unseen protoplanets at the earliest stages of formation, and to reveal the physical processes at play.

First we identify how the tell-tale wake driven by an embedded protoplanet manifests in the midplane dust layer of its host circumstellar disk, and quantify the observing requirements to recover the signal in mm continuum emission with ALMA. These constraints establish the feasibility of mm dust wakes as a protoplanet-detection technique.

Next, we apply our framework to a sample of ten circumstellar disks exhibiting kinematic evidence of wakes in ¹²CO molecular line emission. Such applications are a vital ingredient to distinguishing protoplanetary velocity disturbances from those of non-planetary origin.

We also present the first direct measurement of gravitational instability in a planet-forming disk using ¹³CO and C¹⁸O molecular line emission. Our quantitative constraints on the kinematic structure in a disk with directly-imaged protoplanets demonstrates the physical mechanisms driving planet formation.

Finally, the ¹²CO emission from AB Aurigae exhibits multiple infalling spiral streamers on 1000-au scales. Kinematic modeling pinpoints the region of impact with the disk to be near to candidate protoplanets, suggesting that planet formation cannot be understood without consideration of the surrounding star formation environment.