Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session T3: Active Galactic Nuclei |
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Sponsoring Units: DAP Chair: Stephen S. Holt, Olin College Room: Marriott Tampa Waterside Grand Salon A/B |
Monday, April 18, 2005 1:30PM - 2:06PM |
T3.00001: X-raying Active Galaxies Both Near and Far: Exploring the Environments of Supermassive Black Holes Invited Speaker: X-ray emission appears to be a universal property of active galactic nuclei (AGN). This emission originates primarily in a supermassive black hole's immediate vicinity, and X-ray investigations probe the accretion processes by which black holes grow as well as their larger scale environments. I will review some of the recent dramatic advances made in supermassive black hole studies, obtained using data from NASA's Chandra X-ray Observatory and ESA's X-ray Multi-Mirror Mission-Newton. Specifically, I will discuss (1) X-ray spectroscopy of AGN accretion disks and outflows, (2) ultra-sensitive X-ray surveys that have discovered the highest density and diversity of supermassive black holes throughout the Universe, and (3) X-ray studies of the first supermassive black holes to form in the Universe. Upcoming X-ray missions and some long-term prospects for X-ray astronomy will also be described. Research funding from NASA and NSF is gratefully acknowledged. [Preview Abstract] |
Monday, April 18, 2005 2:06PM - 2:42PM |
T3.00002: Unrobing `Dressed' Black Holes in Galactic Nuclei Invited Speaker: From the event horizon of a massive black hole in a galactic nucleus to the radius on which stars dominate the gravitational potential is a dynamic range of $10^7$. Not surprisingly, the structure of such a galactic nucleus changes greatly over this span of scales. Through a combination of observational data and theoretical reasoning, we now know about many of the principal features. Thick clouds of molecular gas and dust occupy a toroidal region on the largest scale; examples have been interferometrically imaged in the infrared and in H$_2$O maser emission. This toroidal symmetry makes active galactic nuclei differ drastically in appearance depending on our viewing angle. Hot outflowing ionized gas occupies the axial hole in the torus, made visible by polarizing reflection of light from deeper inside and X-ray absorption spectroscopy. A factor of 1000 closer in, UV emission features indicate the presence of cooler ionized gas moving at $0.01c$. In some cases, we see evidence for outflows travelling at $0.1c$ at roughly the same distance scale. Still closer to the center, large-scale numerical simulations now show us how matter flows toward the black hole as a result of magnetic stresses created by internally-generated MHD turbulence. Thermal UV emission and hard X-rays created in coronal regions carry off the accreting matter's lost energy. Immediately outside the event horizon, spinning black holes can seize on the magnetic field created in the flow to transfer their angular momentum to matter in the inflow or drive a relativistic axial outflow. [Preview Abstract] |
Monday, April 18, 2005 2:42PM - 3:18PM |
T3.00003: Gamma-Ray Observations of Active Galactic Nuclei: From GRO to GLAST Invited Speaker: Some fraction of accreting black holes generate powerful collimated relativistic outflows; when these jets are pointed towards us, such Active Galactic Nuclei are known as blazars. Particles in blazar jets radiate in two broad peaks: by synchrotron radiation in the radio to soft X-ray band, and by photons boosted by inverse Compton processes at hard X-ray and gamma-ray energies. Formation of these powerful jets (with bulk Lorentz factor ~10) and the acceleration of particles in the jets (to electron Lorentz factors up to 10$^6$) are not understood - especially since the formation region is too compact to be directly imaged. Our best hope for understanding the jet structure is through multiwavelength variability studies. The upcoming launch of the Gamma-ray Large Area Space Telescope (GLAST), together with current and future X-ray and hard X-ray observatories promise dramatic improvements in data quality. I will review the current observational status, and discuss the advances in understanding we expect from these new capabilities. [Preview Abstract] |
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