All-Sky Radiative Transfer and Characterization for Large-scale Cosmic Structures
Jennifer Y.H. Chan, University College of London
Abstract: In this talk, I will present a fully-covariant formulation of cosmological radiative transfer (RT) for investigating evolving large-scale cosmic structures. Firstly, I will present the covariant formulation for continuum RT, accounting for polarization, and show its full solution. I will show how the cosmological polarized RT calculations are well interfaced with cosmological MHD simulation results to generate maps of the 4 Stokes parameters. Two sets of demonstrations will be shown: (i) pencil-beam calculations using a GCMHD+ simulated galaxy cluster, and (ii) all-sky calculations for a cosmologically-evolving magnetic universe that is modeled using the GCMHD+ outputs. Secondly, I will present the covariant formulation for line RT, focusing on 21-cm line of neutral hydrogen. Similar to the CPRT algorithm, both pencil-beam and all-sky calculations can be carried out straight-forwardly for astrophysical applications. I will present a demonstration on galactic scales, showing its application to diagnose the structures of spiral galaxies. The covariant cosmological RT formulation is generic, applicable (but not restricted) to investigating cosmic magnetism and cosmic reionization, the two key sciences for the Square Kilometer Array (SKA), and other instruments.
An X-ray View of the Innermost Accretion onto Black Holes
Jiachen Jiang, University of Cambridge, UK
Abstract: I will first summarize previous major results from X-ray observations of stellar-mass black holes in X-ray binaries (XRBs) and supermassive black holes (SMBHs) in active galactic nuclei (AGN). The spectra of XRBs and AGN show similar features, including broad Fe K emission line and Compton hump. These features correspond to the reflected emission from the innermost accretion disk. However, previous reflection-based analysis still has some missing pieces, such as a supersolar disk iron abundance. A disk reflection model with a higher disk density might be the solution to these problems. A high disk density model can explain the broad band spectra of XRBs and AGN, and enable to us compare the disk densities at different BH mass scales and accretion rates.