Alexa Gordon (Northwestern University)

Revealing the Progenitor(s) of Fast Radio Bursts through their Environments
Abstract: Fast radio bursts (FRBs) are a new class of highly energetic, extragalactic transients. Despite thousands of FRBs detected to date, many fundamental questions remain, including their progenitor(s) and emission mechanism(s). The ability to localize FRBs to sub-arcsecond precision–pinpointing them to their host galaxies–has revolutionized FRB science by unlocking the wealth of information gleaned from host environments such as stellar mass, age, and star formation rate. In this talk, I discuss how the demographics and diversity of FRB environments lends insight to their progenitor(s) and formation channels. For the most precisely localized FRBs, it is possible to go one step further and study the host properties local to the burst site, including degree of star formation and proximity to galaxy substructure, which are most revealing of the populations that give rise to FRBs. I present a novel formalism to test the underlying spatial distribution of FRBs, quantifying the contribution of various progenitor formation channels. With the advent of new FRB experiments and sensitivity upgrades to current facilities, there will soon be a plethora of precisely-localized FRBs in both the local and distant Universe. I conclude with what we will learn in the era of hundreds of FRB hosts on the global and local environment scales.

Jacob Nibauer (Princeton University)​

Testing Dark Matter with Stellar Stream Dynamics: from the Stellar Halo to Subhalos
Abstract: Stellar streams encode information about the gravitational landscape of galaxies. I will present recent work that leverages stellar stream dynamics to map dark matter in the Milky Way, spanning scales from the global dark matter halo to individual subhalos. First, I will discuss the geometry of the Milky Way’s dark matter halo, using stellar streams as direct tracers of the Galactic acceleration field. The resulting halo mass and shape is inferred without making any prior assumptions about the functional form of the Milky Way’s potential. I will then turn to local fluctuations in the potential, and discuss new results on the number and concentration of low-mass, completely dark matter dominated subhalos. The results highlight a preference for more compact subhalos than expected under the cold dark matter paradigm, and underscore the power of stellar streams for probing the fundamental nature of dark matter. I will conclude by discussing future prospects for constraining dark matter using stellar streams, highlighting the potential of deep photometry from LSST and precision radial velocity data from Via.