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Series

University of Kentucky

2002

Articles 1 - 8 of 8

Full-Text Articles in Physics

He Ii Reverberation In Active Galactic Nucleus Spectra, Mark C. Bottorff, Jack A. Baldwin, Gary J. Ferland, Jason W. Ferguson, Kirk T. Korista Dec 2002

He Ii Reverberation In Active Galactic Nucleus Spectra, Mark C. Bottorff, Jack A. Baldwin, Gary J. Ferland, Jason W. Ferguson, Kirk T. Korista

Physics and Astronomy Faculty Publications

This paper compares the observed reverberation response lags and the intensity ratios of the broad-line region (BLR) emission lines He II λ1640, He II λ4686, and C IV λ1549 with predictions. Published observations indicate that the He II λ1640 lag is 3 times shorter than the lags of He II λ4686 or C IV λ1549. Diverse models, however, do not reproduce this observation. Extensive improved numerical simulations of the hydrogenic isoelectronic sequence emission show that the He II spectrum remains especially simple, even in the central regions of a luminous quasar. Line trapping never builds up a significant population of …

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Temperature Variations From Hubble Space Telescope Imagery And Spectroscopy Of Ngc 7009, R. H. Rubin, N. J. Bhatt, R. J. Dufour, B. A. Buckalew, M. J. Barlow, X.-W. Liu, P. J. Storey, B. Balick, Gary J. Ferland, J. P. Harrington, P. G. Martin Aug 2002

Temperature Variations From Hubble Space Telescope Imagery And Spectroscopy Of Ngc 7009, R. H. Rubin, N. J. Bhatt, R. J. Dufour, B. A. Buckalew, M. J. Barlow, X.-W. Liu, P. J. Storey, B. Balick, Gary J. Ferland, J. P. Harrington, P. G. Martin

Physics and Astronomy Faculty Publications

We present new Hubble Space Telescope (HST)/WFPC2 imagery and STIS long-slit spectroscopy of the planetary nebula NGC 7009. The primary goal was to obtain high spatial resolution of the intrinsic line ratio [O III] 4364/5008 and thereby evaluate the electron temperature (Te) and the fractional mean-square Te variation (tA2)across the nebula. The WFPC2 Temap is rather uniform; almost all values are between 9000–11 000 K, with the higher Te values closely coinciding with the inner He++ zone. The results indicate very small values–≲0.01– for …

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Pumping Or Mixing System Using A Levitating Magnetic Element, Aexandre N. Terentiev Jul 2002

Pumping Or Mixing System Using A Levitating Magnetic Element, Aexandre N. Terentiev

Physics and Astronomy Faculty Patents

A system capable of pumping or mixing relatively warm fluids using a rotating magnetic element or bearing levitated by a cold superconducting element is disclosed. The magnetic element or bearing carries at least one impeller and is placed in a fluid vessel positioned external to the outer wall of a cryostat or other housing for the superconducting element. A separate cooling source thermally linked to the superconducting element provides the necessary cooling to create the desired superconductive effects and induce levitation in the magnetic element or bearing. The outer wall or housing defines a chamber around the cold superconducting element …

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The Physical Conditions Within Dense Cold Clouds In Cooling Flows - Ii, Gary J. Ferland, A. C. Fabian, R. M. Johnstone Jul 2002

The Physical Conditions Within Dense Cold Clouds In Cooling Flows - Ii, Gary J. Ferland, A. C. Fabian, R. M. Johnstone

Physics and Astronomy Faculty Publications

This is a progress report on our numerical simulations of conditions in the cold cores of cooling flow condensations. The physical conditions in any non-equilibrium plasma are the result of a host of microphysical processes, many involving reactions that are research areas in themselves. We review the dominant physical processes in our previously published simulations, to clarify those issues that have caused confusion in the literature. We show that conditions in the core of an X-ray-illuminated cloud are very different from those found in molecular clouds, largely because carbon remains substantially atomic and provides powerful cooling through its far infrared …

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Dust Emission From Active Galactic Nuclei, Maia Nenkova, Željko Ivezić, Moshe Elitzur May 2002

Dust Emission From Active Galactic Nuclei, Maia Nenkova, Željko Ivezić, Moshe Elitzur

Physics and Astronomy Faculty Publications

Unified schemes of active galactic nuclei require an obscuring dusty torus around the central source, giving rise to a Seyfert 1 line spectrum for pole-on viewing and Seyfert 2 characteristics in edge-on sources. Although the observed IR is in broad agreement with this scheme, the behavior of the 10 μm silicate feature and the width of the far-IR emission peak remained serious problems in all previous modeling efforts. We show that these problems find a natural explanation if the dust is contained in approximately five to 10 clouds along radial rays through the torus. The spectral energy distributions of …

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Dissipative Heating And Quasar Emission Lines, Mark Bottorff, Gary J. Ferland Apr 2002

Dissipative Heating And Quasar Emission Lines, Mark Bottorff, Gary J. Ferland

Physics and Astronomy Faculty Publications

Recent observations reveal that the profiles of emission lines of active galactic nuclei are too smooth to be produced by discrete thermal (T~104 K) clouds. The lines may also be too bright to be powered by the continuum unless a large covering factor or additional heating mechanisms are present. We have been investigating one possible explanation of these observations, namely, that the clouds are turbulent. This paper focuses on observational effects caused by dissipation of turbulent energy into cloud heating. We find that internal heating can explain these observations. Clouds energized by both the ionizing continuum and …

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Metallicities And Abundance Ratios From Quasar Broad Emission Lines, Fred Hamann, K. T. Korista, Gary J. Ferland, Craig Warner, Jack Baldwin Jan 2002

Metallicities And Abundance Ratios From Quasar Broad Emission Lines, Fred Hamann, K. T. Korista, Gary J. Ferland, Craig Warner, Jack Baldwin

Physics and Astronomy Faculty Publications

The broad emission lines (BELs) of quasars and active galactic nuclei (AGNs) are important diagnostics of the relative abundances and overall metallicity in the gas. Here we present new theoretical predictions for several UV BELs. We focus specifically on the relative nitrogen abundance as a metallicity indicator, based on the expected secondary enrichment of nitrogen at metallicities Z≳0.2 Z☉. Among the lines we consider, NIII]λ1750/OIII]λ1664, NVλ1240/(CIVλ1549+OVIλ1034), AND NV/HeIIλ1640 are the most robust diagnostics. We argue, in particular, that the average N V BEL is not dominated by scattered Lyα photons from a broad absorption-line wind. We then …

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Fiber Optic Sensor Response To High Levels Of Fat In Cream, Czarena L. Crofcheck, Frederick A. Payne, Clair L. Hicks, M. Pinar Mengüç, Sue E. Nokes Jan 2002

Fiber Optic Sensor Response To High Levels Of Fat In Cream, Czarena L. Crofcheck, Frederick A. Payne, Clair L. Hicks, M. Pinar Mengüç, Sue E. Nokes

Biosystems and Agricultural Engineering Faculty Publications

A light backscatter technique using optical fibers to deliver and receive light was investigated for measuring the milkfat content of unhomogenized cream. Light backscatter through cream at wavelengths of 450 to 900 nm was measured for fiber separation distances from 2 to 6.5 mm and for cream containing 10 to ~40 weight percent (wt%) milkfat. Unhomogenized cream (~40 wt% milkfat) was mixed with skim milk (~0.05 wt% milkfat) to yield samples with five different milkfat levels. Three optical response models were tested for correlation with milkfat content: one using the light intensity measurement at a single separation distance, the second …

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