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Full-Text Articles in Physical Sciences and Mathematics
Megamaser Disks In Active Galactic Nuclei, John F. Kartje, Arieh Königl, Moshe Elitzur
Megamaser Disks In Active Galactic Nuclei, John F. Kartje, Arieh Königl, Moshe Elitzur
Physics and Astronomy Faculty Publications
Recent spectroscopic and VLBI-imaging observations of bright extragalactic H2O maser sources have revealed that the megamaser emission often originates in thin circumnuclear disks near the centers of active galactic nuclei (AGNs). Using general radiative and kinematic considerations and taking account of the observed flux variability, we argue that the maser emission regions are clumpy, a conclusion that is independent of the detailed mechanism (X-ray heating, shocks, etc.) driving the collisionally pumped masers. We examine scenarios in which the clumps represent discrete gas condensations (i.e., clouds) and do not merely correspond to velocity irregularities in the disk. We show …
Oh 1720 Megahertz Masers In Supernova Remnants: C-Shock Indicators, Phil Lockett, Eric Gauthier, Moshe Elitzur
Oh 1720 Megahertz Masers In Supernova Remnants: C-Shock Indicators, Phil Lockett, Eric Gauthier, Moshe Elitzur
Physics and Astronomy Faculty Publications
Recent observations show that the OH 1720 MHz maser is a powerful probe of the shocked region where a supernova remnant strikes a molecular cloud. We perform a thorough study of the pumping of this maser and find tight constraints on the physical conditions needed for its production. The presence of the maser implies moderate temperatures (50-125 K) and densities (~105 cm-3) and OH column densities of order 1016 cm-2. We show that these conditions can exist only if the shocks are of C-type. J-shocks fail by such a wide margin that the presence …