Characterizing the Evolution of Circumstellar Systems with the Hubble Space Telescope and the Gemini Planet Imager
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Date
2017-07-19
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Johns Hopkins University
Abstract
The study of circumstellar disks at a variety of evolutionary stages is essential to understand the physical processes leading to planet formation. As the earliest stage of planet formation, massive, optically thick, and gas rich protoplanetary disks give information about the distribution and composition of the dust grains that will eventually coalesce into planetesimal bodies, while the later stages of the planet formation process (debris disks) demonstrate the interactions that the dust particles in disks have with the planetary bodies.
The recent development of high contrast instruments designed to directly image the structures surrounding nearby stars (e.g. Gemini Planet Imager) and coronagraphic data from the Hubble Space Telescope (HST) have made detailed studies of circumstellar systems possible. As a member of the Gemini Planet Imager (GPI) exoplanet survey team, I have developed the wavelength calibration for the lenslet-based integral field spectrograph. This work has enabled some incredible science, namely the spectral characterization of one of the lowest mass extrasolar planets ever discovered via direct imaging, 51 Eridani b. The second part of this work details the observations and characterization of three systems. I obtained GPI polarization data for the transition disk, PDS 66, which shows a double ring and gap structure and a temporally variable azimuthal asymmetry. This evolved morphology could indicate shadowing from some feature in the innermost regions of the disk, a gap-clearing planet, or a localized change in the dust properties of the disk. Millimeter continuum data of the DH Tau system places limits on the dust mass that is contributing to the strong accretion signature on the wide-separation planetary mass companion, DH Tau b. The lower than expected dust mass constrains the possible formation mechanism, with core accretion followed by dynamical scattering being the most likely. Finally, I present HST observations of the flared, edge-on protoplanetary disk ESO Halpha 569. Using a covariance-based MCMC software toolkit I developed, I combine the scattered light image with a spectral energy distribution to model the key structural parameters such as the geometry (disk outer radius, vertical scale height, radial flaring profile), total mass, and dust grain properties in the disk using the radiative transfer code MCFOST.
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Keywords
exoplanets, circumstellar disks, high contrast direct imaging