Tuesday Lunch Seminar: Yuaguang Chen (Caltech) & Carl Fields (Michigan State University)

Yuaguang Chen (Caltech): Characterizing H I in CGM from Both Emission and Absorption

Abstract: We present new Lyman-alpha observations focusing on the circumgalactic medium of z~2 star-forming galaxies, in both absorption and emission using Keck-LRIS and KCWI.  For absorption, we use the spectra of ~3000 galaxies from the Keck Baryonic Structure Survey (KBSS) to assemble ~200,000 distinct foreground-background galaxy pairs. The ensemble of sightlines and foreground galaxies is used to construct a 2D map of the mean excess Lya optical depth as a function of projected galactocentric distance (20 -- 4000 pkpc) and line-of-sight velocity. We compare the map with the cosmological zoom-in simulation and a simple two-component (inflow + outflow) analytical model. The comparisons suggest that galaxy-scale outflow dominates the H I kinematics within ~50 pkpc, while infall and Hubble expansion dominate at >100 pkpc. For emission, we obtain deep integral field unit observations on ~60 KBSS galaxies. Their Lya spectra in the CGM are compared to the galactic azimuthal angle. We find excess Lya emission along the galaxy major axis within ~30 pkpc. Similar techniques will be used to study metal lines and the relationship between CGM and other host-galaxy properties in the future.

Carl Fields (Michigan State University): Multidimensional Progenitor Models For Core-collapse Supernovae

Abstract: Core-collapse supernova explosions (CCSN) are one possible fate of a massive star. Simulations of CCSNe rely on the properties of the massive star at core-collapse. As such, a critical component is the realization of realistic initial conditions. Multidimensional progenitor models can enable us to capture the chaotic nuclear shell burning occurring deep within the stellar interior. I will discuss ongoing efforts to progress our understanding of the nature of massive stars through next-generation hydrodynamic stellar models. In particular, I will present recent results of three-dimensional hydrodynamic models of massive stars evolved for the final moments before collapse. These recent results suggest that realistic 3D progenitor models can be favorable for obtaining robust models of CCSN explosions and are an important aspect of massive star explosions that must be taken into consideration. I will conclude with a brief discussion of the implications our models have for accurate predication of multi-messenger signals from CCSNe such as gravitational wave emission.