Complex Spiral Structure in the HD 100546 Transitional Disk as Revealed by GPI and MagAO

Abstract

We present optical and near-infrared high-contrast images of the transitional disk HD 100546 taken with the Magellan Adaptive Optics system (MagAO) and the Gemini Planet Imager (GPI). GPI data include both polarized intensity and total intensity imagery, and MagAO data are taken in Simultaneous Differential Imaging mode at Hα. The new GPI H-band total intensity data represent a significant enhancement in sensitivity and field rotation compared to previous data sets and enable a detailed exploration of substructure in the disk. The data are processed with a variety of differential imaging techniques (polarized, angular, reference, and simultaneous differential imaging) in an attempt to identify the disk structures that are most consistent across wavelengths, processing techniques, and algorithmic parameters. The inner disk cavity at 15 au is clearly resolved in multiple data sets, as are a variety of spiral features. While the cavity and spiral structures are identified at levels significantly distinct from the neighboring regions of the disk under several algorithms and with a range of algorithmic parameters, emission at the location of HD 100546 "c" varies from point-like under aggressive algorithmic parameters to a smooth continuous structure with conservative parameters, and is consistent with disk emission. Features identified in the HD 100546 disk bear qualitative similarity to computational models of a moderately inclined two-armed spiral disk, where projection effects and wrapping of the spiral arms around the star result in a number of truncated spiral features in forward-modeled images.

Spiral Arms in Disks: Planets or Gravitational Instability?

“…We adopt M å =2.3 M ☉ and R å =2.6 R ☉ . Follette et al (2017) showed that processing a total intensity image of a modestly inclined disk with a small number of spiral arms with angular differential imaging (ADI) techniques may increase the number of arms by breaking them into pieces. The arms seen in the HD 100546 disk may be susceptible to this effect.…”

Cloudlet capture by transitional disk and FU Orionis stars

“…Quillen (2006) suggest that the spiral patterns can be explained by illumination from the star if the disk is warped. HD 100546 has also been known to feature an inner hole of about 13 AU radius (Bouwman et al 2003;Grady et al 2005), later confirmed in the direct imaging at optical and infrared wavelengths (Garufi et al 2016;Follette et al 2017), thus clearly making it a Transition Disk. It must also have at least some material close to the star (around 0.5 AU distance, where the dust sublimation radius is), owing to its observed nearinfrared excess.…”

Clarifying the Status of HD 100546 as Observed by the Gemini Planet Imager

“…a full-rank LOCI) preclude robust detections of either source and much of the disk. Rigorous forward-modeling employed in Currie et al (2015) but not considered in Follette et al (2017) provided evidence that "c" is a real astrophysical feature even if the interpretation (disk feature or protoplanet) is unclear.…”

“…Our A-LOCI (Currie et al 2012) and KLIP reductions have high throughput (> 70%-80% for 'b'). The detections of "c" are not due to aggressive processing as proposed in Follette et al (2017). Instead, aggressive settings (i.e.…”