Imaging Discovery of the Debris Disk Around Hip 79977

Abstract

We present Subaru/HiCIAO H-band high-contrast images of the debris disk around HIP 79977, whose presence was recently inferred from an infrared excess. Our images resolve the disk for the first time, allowing characterization of its shape, size, and dust grain properties. We use angular differential imaging (ADI) to reveal the disk geometry in unpolarized light out to a radius of ∼2 ′′ , as well as polarized differential imaging (PDI) to measure the degree of scattering polarization out to ∼1. ′′ 5. In order to strike a favorable balance between suppression of the stellar halo and conservation of disk flux, we explore the application of principal component analysis (PCA) to both ADI and reference star subtraction. This allows accurate forward modeling of the effects of data reduction on simulated disk images, and thus direct comparison with the imaged disk. The resulting best-fit values and well-fitting intervals for the model parameters are a surface brightness power-law slope of S out = −3.2 [−3.6, −2.9], an inclination of i = 84 • [81 • , 86 • ], a high Henyey-Greenstein forward-scattering parameter of g = 0.45 [0.35, 0.60], and a non-significant disk-star offset of u = 3.0 [−1.5, 7.5] AU = 24 [−13, 61] mas along the line of nodes. Furthermore, the tangential linear polarization along the disk rises from ∼10% at 0. ′′ 5 to ∼45% at 1. ′′ 5. These measurements paint a consistent picture of a disk of dust grains produced by collisional cascades and blown out to larger radii by stellar radiation pressure.

The Matryoshka Disk: Keck/Nirc2 Discovery of a Solar-System-Scale, Radially Segregated Residual Protoplanetary Disk Around Hd 141569a

“…i.e., those fulfilling 2 c min 2 c + N 2 data binned (Thalmann et al 2013), which for our case implies 2 c n 1.124. The best-fit model accurately reproduces the disk morphology (Figure 2) and, when subtracted from the Keck image, nulls its signal, including the point-source-like peak, but leaves the hook-like features largely intact (SNRE ∼ 3.5-4.5 in the residual image).…”

Polarimetry and flux distribution in the debris disk around HD 32297

“…The ADI technique complemented by principal component analysis (PCA) is then used, which reconstructs the PSF of the central star from a library of reference PSFs and subtracts it from the target image (Soummer et al 2012). This is the so-called PCA-ADI technique that permits forwards modelling of astronomical sources, such as circumstellar disks, which in some cases has proven better at removing certain systematic noise patterns (see Thalmann et al 2013) than the locally optimized combination of images (LOCI, Lafrenière et al 2007) and seems to yield similar S/N images (e.g. Meshkat et al 2013).…”

“…The ADI approach is completed by derotating all the images according to their individual parallactic angle and collapsing them together into one single final PCA-ADI image for every subtracted mode. The mean is used in our reduction instead of the median to assure linearity of the data (Thalmann et al 2013;Brandt et al 2013). After visual inspection of the output images, we concluded that the subtraction of five modes out of 53 provides a good balance between flux self-subtraction and speckle noise suppression.…”

The architecture of the LkCa 15 transitional disk revealed by high-contrast imaging

“…For highly inclined and well resolved circumstellar disks, the radial noise profile can be measured in sectors of the final science image unaffected by the disk flux (e.g., Thalmann et al 2011Thalmann et al , 2013. However, the crescent of scattered light from the LkCa 15 disk, as well as the surrounding oversubtraction regions, dominate our ADI images at all position angles, which renders it impossible to measure an unbiased noise profile.…”

“…For point sources, this effect is easy to determine (e.g., Lafrenière et al 2007;Brandt et al 2013), but the subtraction effects are non-trivial for extended sources such as disks and can affect the apparent morphology of the source. Forward modeling is a powerful tool for interpreting these images and extracting the disk geometry (e.g., Thalmann et al 2011Thalmann et al , 2013Milli et al 2012).…”