Astrophysics Brown Bag Lunch Talk 10/24/2022: Speakers: Dylan Jow (U Toronto) And Xuejian (Jacob) Shen (Caltech)

In Person in Marlar and/or Virtual Brown Bag Lunch 
Monday October 17, 2022 at 12:00 Link Below
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Presentation in Marlar 37-252/37-272 for those wishing to attend in person


Dylan Jow, University of Toronto at 12:05 (in person )

Wave-optics in astrophysical lensing: unlocking the potential of the coherent sky
Abstract: The lensing of coherent sources, such as FRBs and pulsars, has the potential to be a powerful cosmological and astrophysical probe. In particular, with the abundance of FRB data we are set to obtain, gravitationally lensed FRBs may be used to constrain compact dark matter over a wide range of masses, as well as probe cosmic expansion in real time. However, the theory of wave optics needed to describe the lensing of coherent sources is underdeveloped. In addition, scattering due to plasma along the line of sight may limit the sensitivity of gravitationally lensed FRBs as a cosmological probe. We will discuss advancements in the theory of wave optics as applicable to astrophysical lensing (plasma and gravitational), in particular the application of Picard-Lefschetz theory for the evaluation of the Kirchoff diffraction integral. We will also describe progress in understanding the origin of pulsar scintillation due to scattering in the ISM and its implications for modeling FRB scattering.

Bio: I am a PhD student in my final year working with Ue-Li Pen at the Canadian Institute for Theoretical Astrophysics. My research focuses on gravitational and plasma lensing in radio astronomy, and in particular how we can use these tools to learn about cosmology, the ISM and the IGM.

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Xuejian (Jacob) Shen at 12:30 pm (in person)

Alternative dark matter models in the context of galaxy formation

Abstract:  In this talk, I will briefly review the motivation & history of studying dark matter (DM) models alternative to WIMP-like CDM, and introduce our recent studies of some physically well-motivated models that are less explored in the astrophysical context. These include i) hidden-sector DM models with dissipative self-interactions; ii) the post-inflationary QCD axions. In the second half of the talk, I’ll bring the attention to studying alternative DM in regimes, where we expect significant improvements in understanding relevant baryonic astrophysical processes from a combination of observational and theoretical developments in the next decade.

Bio:  I am a 5th-year PhD candidate in Physics at the California Institute of Technology, working with Prof. Philip Hopkins. I am an active member of the FIRE collaboration. My primary research interest is studying galaxy formation & evolution in dark matter models alternative to the classical CDM, using a combination of semi-analytical models and numeric simulations. During the early years of my PhD, I worked on an observational determination of the bolometric quasar luminosity functions and a series of work on high-redshift galaxy predictions from the IllustrisTNG simulation.


Event Contact

Josh Borrow