A Uniform Analysis of Directly Imaged Debris Disks

Second-generation, high contrast imaging instruments such as the Gemini Planet Imager (GPI) provide the highest angular resolution maps of the scattered light from dust in debris disks. The intensity of the scattered light depends not only on the density of the dust grains but also on their scattering phase functions (SPFs), complicating the interpretation of the GPI images. We are pursuing a study to disentangle the disk geometry and scattering phase function for one dozen bright debris disks observed with the 87-hour GPI Large 87-hour Gemini Large and Long Program (LLP) Characterizing Dusty Debris in Exoplanetary Systems (PI: Chen, Project GS-2016-LP-6). Combined with the existing observations from the Gemini Planet Imager Exoplanet Survey (GPIES), we now have full 1 through 2.2 micron coverage of all targets. Our ongoing data analysis and modeling program is designed to perform a uniform study of debris disks spatially resolved in total intensity and polarized light to characterize key properties of disk geometry and SPFs that are related to the evolution of planetary systems. Disk properties will be constrained using the radiative transfer disk modeling code MCFOST. For example, measuring the radial and vertical extent of disks is an essential component of understanding the evolutionary history of a planetary system. Ultimately, the results of this study will increase the number of disks with measured unpolarized SPFs by a factor of >2 and the number of disks with polarized SPFs by a factor of >5. The limited number of SPFs measured in total intensity thus far exhibit a very unexpected nearly universal phase function for debris disks and the Solar System, regardless of their circumstellar environment. Extracting both polarized and unpolarized SPFs from a large sample of disks is a key goal of this study and will investigate the diversity or universality of SPFs and how they differ between star systems of a range of ages and spectral types. This poster will present the imaged sample and the initial phase of the project, utilizing MCFOST to assume fixed scattering phase functions and determining the geometric properties.