Galaxies and Cosmology Seminar

Om Gupta, The University of Texas at Austin

Fast Radio Burst Circular Polarization Arising in Magnetar Wind

Fast Radio Bursts are millisecond duration extragalactic radio transients discovered in 2007. Their observed morphology and spectrum retain valuable information about their interactions with intervening plasma and about conditions near the source. Some FRBs are observed to have circular polarization. Assuming that the circular component arises from a propagation effect known as Faraday conversion, we develop a realistic model of a magnetar wind where this phenomenon can occur. This model naturally explains why most bursts do not exhibit circular polarization, and provides source environment constraints even when no circular polarization is observed. Furthermore, we extract vital information about the wind environment by fitting the spectral variations of observed circular polarization. The highly testable and falsifiable predictions of our model allow us to identify bursts where special conditions in the wind, contributions from the magnetosphere, or intrinsic properties of the burst deviate the observed polarization from our predictions. In this talk, I will also highlight key concepts from laser physics that form the backbone of this model.

Resherle Verna, The University of Texas at Austin

Spatially Resolved Mapping of Density and Mass in M82’s Starburst Outflow with VIRUS-P

Galactic outflows are a critical mechanism for feedback in star-forming galaxies, capable of removing gas, suppressing future star formation, and enriching the circumgalactic medium. However, empirical constraints on the mass and structure of these outflows—particularly in the warm ionized phase—remain limited due to their diffuse and spatially extended nature. This presentation features results from 28 nights of VIRUS-P integral field observations of M82’s northern outflow. M82 is a nearby (3.5 Mpc), edge-on starburst galaxy with a well-known bipolar wind, making it an ideal laboratory for spatially resolved outflow studies. With VIRUS-P’s wide field of view (2.89 arcmin²) and sensitivity to low surface brightness emission, we trace the outflow to several kiloparsecs above the disk. Electron densities are derived from the [S II] λλ6717,6731 doublet, and combined with extinction-corrected Hα luminosities to estimate the mass of warm ionized gas. Initial results reveal coherent radial density gradients and a declining mass profile with increasing distance from the disk. These measurements allow us to empirically test assumptions in mass outflow rate calculations, provide insight into the geometry and structure of the outflow, and offer a valuable benchmark for comparisons to simulations of starburst-driven winds.