报告摘要：The Seyfert 2 galaxy NGC 5728 exhibits x-ray emission over a region ∼ ±1kpc in extent, including a broad (∼ 30,000 km/s) line at 6 keV as well as slower (∼ 1,000 km/s) outflow in [O III] and other low ionization state ions, and an even slower outflow in molecular gas. I will show that the ions producing the 6 keV line emission come from material that is not strongly coupled to the ambient (probably also outflowing) gas. I will argue that most of the emitting material is embedded in dust grains that are decoupled from the gas, and driven outward by radiation pressure from the big blue bump of the central AGN. The grains can be accelerated in a time shorter than the grain sputtering or shattering time, with a modest fraction of the Fe (and other) atoms being separated from the grains. The sputterd Fe atoms will produce the observed Fe Lyman alpha emission. The kinetic luminosity and momentum outflow rate are orders of magnitude lower than would be inferred using models of ultra-fast outflows of similar velocity. If this result holds for other UFOs, it will alter our current understanding of AGN feedback, removing one possible channel.
主讲人简介：Norman Murray obtained his B.Sc. at Caltech, followed by a Ph.D. at Berkeley. After postdoctoral positions at Queen Mary College London, and then at Caltech, he joined the faculty at the Canadian Institute for Theoretical Astrophysics in 1993. Murray works on a broad range of problems in astrophysics, including planetary dynamics, solar oscillations and magnetic fields, black holes and their effects on their host galaxies, as well as planet, star, and galaxy formation. He has made significant contributions to the theory of outflows from supermassive black hole accretion disks (broad absorption line quasars), the theory of stellar feedback on star and galaxy formation, and on photo-evaporative atmospheric loss from planets. He explained why the giant planets in our Solar System are chaotic, and why some hot Jupiters orbit their host stars in highly inclined or even retrograde orbits. He has also worked on the theory of thermal tides on Earth and on exoplanets. Murray was involved in the construction of Bob Leighton's 10 meter sub-millimeter dishes, one of which is currently in use by the COMap collaboration (of which he is a member) as well as the ongoing construction of the Fred Young Submillimeter Telescope to be installed at the CCAT-prime observatory near the summit of Cerro Chajnantor, in 2025.
