Deborah Lokhorst

In the reigning cosmological theoretical model (lambda-CDM), the cosmic web is the largest structure in the Universe: a foam-like structure of dark matter that dictates where structures made out of "normal" matter, such as planets and stars, will form.

Galaxies form in the nodes of the cosmic web, but the majority of gas (the building block for galaxies) remains in the filaments of the cosmic web (the intergalactic medium). Gas is believed to transition from the filaments to the circumgalactic medium of galaxies, then from there into the galaxies themselves. How these steps happen, though, remains largely a mystery.

The Dragonfly Filter-Tilter

The circumgalactic medium is a large, diffuse structure with extremely low surface brightness emission. This places it squarely in the regime of the Dragonfly Telephoto Array, but instead of stars, Dragonfly needs to be able to observe gas.

Deb designed the Dragonfly Filter-Tilter, which enables an optical ultra-narrow bandpass filter to be mounted in front of the optics. In additional the Filter-Tilter has the robotic ability to rotate the filter with respect to incoming light, which shifts the wavelength of light that is allowed through the filter. This allows a larger range of astronomical targets to be investigated with the same filter.

Deb is a Team Leader for a massive upgrade to the Dragonfly Telephoto Array which is currently underway that will add on this ultra-narrowband imaging capability to Dragonfly. Dragonfly will be expanded from 48 to 168 telephoto lenses, 120 of which will be equipped with Filter-Tilters and ultra-narrow bandpass filters. This expansion to Dragonfly is called the Dragonfly Spectral Line Mapper. The Dragonfly Spectral Line Mapper (DSLM) is currently under construction with an anticipated completion date at the end of the summer of 2023.

The DSLM is being built in stages and during her PhD, Deb constructed a pathfinder version with three lenses. She used the pathfinder to carry out an imaging campaign on the M81 group of galaxies, the results of which were published in 2021 and 2022. Using this data, the team discovered a giant shell of gas in the outskirts of the M82 galaxy (the "H-alpha Shell" - pictured on the left). Once the DSLM is on sky, it will carry out an imaging campaign to map out the circumgalactic medium of local galaxies.

The Dragonfly Telephoto Array is a powerful low surface brightness emission wide-field imager. It was designed and constructed by Prof. Bob Abraham at the University of Toronto and Prof. Pieter van Dokkum at Yale University. With a mosaic design formed by multiplexing 48 Canon Telephoto lenses together, Dragonfly is fully refracting, which enables it to reach an order of magnitude fainter in surface brightness imaging than other facilities. During her PhD, Deb helped to build Dragonfly along with a number of fellow graduate students, including software and hardware work on the telescope as well as developing the data reduction pipeline.

During her PhD, Deb led the graduate student outreach group AstroTours, which runs monthly public outreach events including a public lecture, planetarium shows, observing, and demos. Since then, she has continued with outreach, giving regular public talks about current research on research on dark matter, telescopes, and galaxies to a variety of audiences.

A couple of these talks have been recorded and can be watched from these links:

• Astrotours (August 2018)
• Edmonton RASC (May 2021)