Astronomy Tea Talk
Speaker 1: Lizhong Zhang (postdoctoral research fellow; Institute for Advanced Study and the Center for Computational Astrophysics)
Title: Luminous Black Hole Accretion: How Radiation and Magnetic Fields Regulate Accretion Flows
Abstract: Radiation and magnetic fields play crucial roles in shaping the structure and dynamics of luminous black hole accretion flows. We study these systems by solving the general relativistic magnetohydrodynamic (GRMHD) equations coupled with angle-dependent radiation transport, which provides a self-consistent framework for modeling accretion from super- to sub-Eddington regimes. At super-Eddington rates, strong radiative support vertically inflates the accretion disk, forming a geometrically thick flow with a narrow polar funnel, through which radiation escapes inefficiently. At sub- and near-Eddington rates, disks become geometrically thin and their structure is set by magnetic field topology: (1) a thin thermal disk embedded within a magnetic envelope when sufficient net vertical magnetic flux is present, or (2) a magnetically elevated disk when the vertical flux is weak or absent. Our simulations reproduce observed trends and provide predictive diagnostics for radiation-dominated black hole accretion systems.
Speaker 2: Alex Haughton (PhD candidate; University of Colorado, Boulder)
Title: INFUSE II - science and upgrades for the second launch of the far ultraviolet integral field spectrograph
Abstract: The Integral Field Ultraviolet Spectroscopic Experiment (INFUSE) sounding rocket is the first image-slicer based far ultraviolet integral field spectrometer and a pathfinder for an IFS mode on Habitable Worlds Observatory. The first launch of INFUSE occurred from White Sands Missile Range on October 29th, 2023, and demonstrated spectral multiplexing, successfully detecting ionized gas emission in the XA region of the Cygnus Loop. The second launch of INFUSE will observe our nearest known Green Pea analog, dwarf galaxy NGC 2366, alongside companion NGC 2363. The 2.5' x 2.5' FOV of INFUSE will map the C IV and O VI lines at a spatial resolution of about 6" spaxels, revealing the morphology of the hot ionized gas. A number of upgrades have been made to INFUSE since the first launch, including a new xenon-enhanced lithium fluoride coated image slicer and grating, improved vacuum sealing, a getter pump, coatings to reduce scatter, redesigned baffles, and a new grating array. The ride along Spectroscopic Multi-Object Observatory has also been integrated into the payload.