My research is broadly focused on star and planet formation studies, including searching for low mass companions around a range of stars, imaging very young stellar disks at short separations, and developing imaging / wavefront sensing algorithms. The following is a list of some of my projects:
Commissioning the Gemini Planet Imager’s Non-Redundant Mask (NRM) mode
The Gemini Planet Imager is a high contrast instrument on Gemini South with an integral field unit spectrograph and polarimeter observing in Y-K bands. In its coronagraphic, direct, or NRM modes it can measure either a spectrum or two orthogonal polarization channels at every location in the image defined by a lenslet array at its focus. My main role on the GPI team has been to commission the NRM mode by designing and analyzing observations in a range of conditions and instrument configurations that use the mask. In spectroscopy mode, GPI’s NRM is very powerful for finding moderate contrast companions (contrast ratios of ~1e-3) that are ~20-150 mas separated from the parent star, a region that is otherwise blocked by the coronagraphic mask. In polarimetry mode GPI’s NRM can take advantage of differential visibilities between polarization states to measure disk polarization that varies in azimuthal angle around the star at similar close separations. These polarimetric observations can recover structure around young stars with tight inner disks, evolved stars shedding their envelopes, and other challenging scenes to image.
GPI’s NRM measured the position of the M-dwarf companion to transitional disk HD 142527.
Predicting performance with NIRISS-AMI and preparing for early JWST
The Near InfraRed Imager and Slitless Spectrograph (NIRISS) instrument on JWST has a special imaging mode called Aperture Masking Inteferometry (AMI). I started my PhD work thinking about understanding sources of error in NIRISS-AMI data analysis and looking at the first images to come out of cryovacuum tests. One of my major roles in UM Astronomy’s Formation and Evolution of Planetary Systems group is to help define observing programs that will showcase AMI capabilities.
AMI will be a great tool for studying the inner regions (<200 mas) of transitional disks, AGN, and evolved stars.
Wavefront sensing with in-focus images
I also work developing wavefront sensing methods for both ground and space telescopes. I recently published a simple phase retrieval method using two images — one with NIRISS’s aperture mask and one with its full pupil. This does not require any moving mirrors, or introducing any focus. It could simplify phasing and aligning of segmented space telescopes. I am exploring ways to extend this to a single image approach that takes advantage of pupil asymmetries. My python code is available on github.
Forward modeling KLIP PSF subtraction
More recently I’ve been working on developing and testing KLIP (Soummer, Pueyo, & Larkin 2012) forward modeling (Pueyo 2016) for spectral extraction in IFU data for imagers like GPI and SPHERE. The forward model estimates the contribution of the companion signal in the reference frame that will lead to over- and self-subtraction. I am working with other developers of the pyklip package to include spectral extraction tools that use this forward modeling.
You can see recent results using this method to extract spectra of the HR 8799 planets c, d, and e.
