Secrets in Stellar Halos: Imaging Against the Glare

Abstract

The imaging of astronomical objects at extremely high angular resolution is an invaluable tool for myriad areas of astronomy, including the study of protoplanetary disks, mass-loss of evolved stars and AGN. But this poses a significant technical challenge as Earth’s turbulent atmosphere massively degrades the resolution achievable by large telescopes. In this thesis the development and implementation of two novel techniques to overcome this seeing limit are presented, building upon the technique of astronomical interferometry. First, differential polarimetry is combined with aperture-masking interferometry to produce diffraction-limited measurements of polarised structure (such as protoplanetary disks and evolved-star mass-loss shells) at precisions well beyond conventional aperture-masking. Observations using this technique are presented, and the development of an entirely new, purpose-built instrument - VAMPIRES - is described (now at the 8 m Subaru telescope). First on-sky tests and science observations are also presented. The second technique described replaces the traditional aperture mask with photonic pupil-remapping technologies. In this instrument - Dragonfly - optical waveguides inscribed in three dimensions within a photonic chip (using laser direct-write) are used to re-map an arbitrary set of telescope sub-apertures into a one-dimensional output, yielding several advantages. The requirement for a non-redundant input is removed, potentially allowing the entire telescope pupil to be utilised, vastly increasing throughput. The waveguides are single-moded, acting as a spatial filter and greatly improving closure phase precision. This output configuration is then ideal for a photonic beam combiner chip or direct fringe production, and spectral dispersion. Various technical challenges and their characterisation and mitigation are also presented. Together, these technologies stand to play a key role in high angular resolution, high contrast astronomical imaging.