Directly Imaging Circumstellar Debris Disks

Debris disks are a collection of dust grains and planetesimals around a star and are thought to contain the remnants of planet formation. Directly imaging debris disks and studying their morphologies is valuable for studying the planet formation process. In some stellar systems that have a directly imaged debris disk, there are also directly imaged planets. Debris disk structures like gaps and asymmetries can show the gravitational e↵ects of planets that are below the brightness threshold for being detected via direct imaging. We investigate a sample of debris disks in Scorpius-Centaurus (Sco-Cen) that were imaged with the Gemini Planet Imager (GPI), which is an adaptive optics system with a coronagraph to block starlight. We look at two GPI data sets, the GPIES campaign Sco-Cen targets, and a follow-up observing program for Sco-Cen targets. We resolve 5 debris disks in the follow-up program and 13 from the GPIES campaign. By calculating contrast curves, we determine the planet detection limit in each of the GPI images. We find that we could have detected 5 Jupiter mass planets at angular separations greater than about 0.6 arcseconds in our GPIES campaign images. In three of our images we could have detected 2 Jupiter mass planets in wide orbits, but 2 Jupiter masses below the detection limit in our other images. We identify one point source around HD 108904 as a sub-stellar companion candidate. To further check for evidence of planets that are below the detection limit, we measure the surface brightness profile of the disks to check for asymmetries in brightness. We find that one of the edge-on disks has an asymmetric surface brightness profile, HD 106906, and three other edge-on disks have symmetric surface brightness profiles. We also find that two disks, HD 106906 and HD 111520, are asymmetric in radial extent, which is possibly evidence for gravitational interactions with planets.