Characterizing young debris disks through far-infrared and optical observations
Donaldson, Jessica Kate
Hamilton, Douglas P
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Circumstellar disks are the environments where extrasolar planets are born. Debris disks in particular are the last stage of circumstellar disk evolution, the youngest of which may harbor still-forming terrestrial planets. This dissertation focuses on examining the properties of dust grains in the youngest debris disks as a proxy to study the unseen parent planetesimal population that produces the dust in destructive collisions. The parent planetesimals are important to understanding the late stages of terrestrial planets because they can deliver volatile material, such as water, to young terrestrial planets. We used the Herschel Space Observatory to study young debris disks (ages 10-30 Myr) in the far-infrared where the thermal emission from the dust grains is brightest. We constructed spectral energy distributions (SEDs) of 24 debris disks and fit them with our debris disk models to constrain dust parameters such as temperature, dust location, and grain size. We also looked for correlations between the stellar and disk parameters and we found a trend between the disk temperature and stellar temperature, which we fit as a power-law. One bright, well studied disk in our sample, HD32297, has a well populated SED, allowing us to fit it with a more detailed model to determine dust grain composition. The HD32297 disk has also been imaged in scattered light, so we used the image to constrain the dust location before fitting the SED. We found the dust grains are composed of a highly porous and icy material, similar to cometary grains. This suggests there are icy comets in this system that could deliver water to any terrestrial planets in the disk. We followed up this system by observing it with the Hubble Space Telescope to get simultaneous spatial and spectral data of the disk. These data let us look for compositional changes with disk radius. We found the disk has a very red color at optical wavelengths in the innermost radius we probed (110 AU). This could indicate the presence of organic material, or it could be a property of the scattering phase function of large grains. Further analysis of this data is ongoing.