Myles Sherman (Caltech)

Searching for Long-Period Radio Transients with the DSA-110
In this talk, I will describe the design and commissioning tests for the DSA-110 Not-So-Fast Radio Burst (NSFRB) search pipeline, a 1.4 GHz image-plane single-pulse search sensitive to 134 ms-160.8 s radio bursts. Extending the pulse width range of the DSA-110 Fast Radio Burst (FRB) search by 3 orders of magnitude, the NSFRB search is sensitive to the recently-discovered Galactic Long Period Radio Transients (LPRTs). The NSFRB search operates in real-time, utilizing a custom GPU-accelerated search code implemented in Python with JAX. In addition to successful commissioning observations of continuum sources and pulsar B0329+54, we conducted an offline DSA-110 NSFRB Galactic Plane Survey (DN-GPS) for LPRTs. The results are used to place informative constraints on the LPRT populations in the Galactic Plane and compare the leading progenitor models: the White Dwarf-M Dwarf binary model and the isolated magnetar model.

Isabel Sands (Caltech)​

Modeling Diffuse Gamma-Ray Emission in MHD Galaxy Formation Simulations with Full Cosmic Ray Spectra: Lessons for the Galactic Center and Beyond
Over the last few decades, observations of diffuse gamma-ray emission in the Milky Way have challenged astrophysical models– in particular, the excess of GeV gamma-rays detected in the Milky Way’s galactic center, and the massive gamma-ray bubbles (the “Fermi bubbles”) centered about the Milky Way’s disk. Nearly all past studies of galactic gamma-ray emission make simplifying assumptions about CR propagation that may not be valid (e.g., steady-state equilibrium), but recent numerical breakthroughs have enabled fully time-dependent dynamical evolution of CRs in magnetohydrodynamic (MHD) simulations with resolved, multi-phase small-scale structure in the ISM, allowing self-consistent comparisons to the Milky Way observations. In this talk, I will present new work in which we model gamma ray emission in simulations of Milky Way-mass galaxies with fully-resolved, multi-species cosmic ray spectra. We find that the gamma ray spectrum in the galactic center can fluctuate by up to an order of magnitude on million-year timescales due to highly variable star formation and losses from variable structure in the turbulent ISM. Some fluctuations are consistent with the measured Fermi-LAT excess. I will also show that Fermi bubble-like features arise from stellar feedback in these simulations and are linked to galactic fountain flows. Finally, I will briefly discuss how this work connects to the circumgalactic medium, and will enable new constraints on cosmic ray transport.