High-Contrast Imaging

One of the biggest obstacles to direct imaging of exoplanets and circumstellar disks is the high contrast between those objects and the host star, which can be several orders of magnitude brighter. Angular differential imaging (ADI) is a state-of-the-art observing and image processing technique developed to suppress that starlight. However, when applied to extended objects such as disks, ADI has the effect of subtracting flux from the disk, as well. This "self-subtraction" is undesirable because it biases subsequent measurements of the disk's surface brightness, upon which inferences about the disk's morphology and composition are made.

My collaborators and I have developed a new technique to forward-model and correct for this self-subtraction of extended emission. Requiring only a model of the disk's underlying brightness distribution, the parallactic angles of the ADI data set, and the parameters used in the ADI (or LOCI) image processing, the algorithm quickly and accurately computes the location and amplitude of self-subtraction. Thus, we can account for the spatially-dependent flux loss and make unbiased measurements of the disk surface brightness. See Esposito et al. 2014 for full details.