Mawson W. Sammons Ph.D.

About

My name is Dr. Mawson Sammons, I am an astrophysicist and radio astronomer at McGill University's Trottier Space Institute in Montreal, Canada. I specialise in transient radio astronomy, particularly in the study of Fast Radio Bursts. I am keenly interested in understanding how FRBs propagate through our Universe, and how the study of gravitational lensing and diffractive scattering in FRBs can be used to probe the nature of dark matter and extragalactic plasma. For more have a look here.

I've held the Trottier Fellowship at McGill since October 2023 where I've been part of the CHIME & CHORD collaborations. Prior to McGill I recieved my Ph.D. from Curtin University in Perth, Australia, where I worked with the CRAFT team on FRBs detected by ASKAP, under the supervision of Prof. Cathryn Trott, Dr Clancy James, Dr Mark Walker and Prof. Jean-Pierre Macquart.

Outside of work I can found soaking up those summer rays on a hike or a climb, or sheltering inside with X-Files on repeat through those colder winter nights.

Research

From the image of an office plant to the explosion of a distant star, all signals are affected by the environments through which they propagate. As a result the signals we observe often contain information about those environments, like the height of beach waves reflecting the depth of the water below. By understanding precisely how those envrionments affect our signals we can extract this information and hopefully learn something new. This principle is an extremely valuable tool for investigating environments which do not produce any signals of their own, such as dark matter or cold intergalactic plasmas. Furthermore transient signals like FRBs serve as the perfect signal, like a sharp sonar ping with which we can map the Universe.

My research focusses primarily on building our understanding of how gravitational lensing and diffractive scattering will affect FRB signals, and extracting envrionmental information about dark matter or cold plasmas. A full record of my published studies can be found here but the basic principles are oft encountered in our everyday lives.

Gravitational lensing occurs when light passes by a massive object. Just as a ball would drop to the ground, so too does light fall towards the centre of that object. Normally, the light travels so quickly as to escape this pull, resulting in a simple deflection from its intended path. All these deflection towards the centre of that object act like a focussing lens in precisely the same way as the reflections do on the inside of the above pint glass. This focussing magnifies the image we see, making it appear larger, and also making it easier to detect. In a recent publication some colleagues and I showed that this magnification from gravitational lensing by the largest structures in our Universe, galaxy clusters, could be used to look for the most distant FRBs ever.

Diffractive scattering is perhaps an even more fundamental and commonplace phenomena. It occurs when waves, like those traversing the rockpool above encounter something in their path that changes their direction. Different parts of the wave that deflected around a jutting rock or a cold plasma cloud can interfere with one another at the observer to cause a flucturation in the ampltidue of the wave we see. This same phenomena causes the stars to twinkle in the night sky, and also causes FRBs to twinkle through our Galaxy's interstellar plasma. By applying the same principles seen for atmospheric scintillation to FRBs we can extract the position of scattering mediums and help to understand the environment local to FRBs.

Teams

Since starting as a postdoctoral fellow I have been a member of both the CHIME and CHORD collaborations. Beginning as strictly a hydrogen intensity mapping experiment, CHIME has swiftly become one of the worlds leading facilities in FRB detection and comprises some of the foremost experts in the FRB field. CHORD is in construction instrument designed from the wealth of experience built by CHIME, as a purpose-built instrument we expect it will detect FRBs an order of magnitude faster than CHIME and over a broader bandwidth, providing the data for the next generation of FRB astronomy.

Contact

Email: mawson.sammons@mcgill.ca

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Elements

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