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- Keyword
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- GALAXIES: QUASARS: EMISSION LINES (2)
- Galaxies: Quasars: Emission Lines (2)
- ISM: ABUNDANCES (2)
- ISM: Abundances (2)
- COSMOLOGY: LARGE-SCALE STRUCTURE OF UNIVERSE (1)
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- Cosmology: Large-Scale Structure of Universe (1)
- GALAXIES: QUASARS: GENERAL (1)
- GALAXIES: SEYFERT (1)
- Galaxies: Quasars: General (1)
- Galaxies: Seyfert (1)
- ISM: ATOMS (1)
- ISM: Atoms (1)
- ISM: H II REGIONS (1)
- ISM: H II Regions (1)
- ISM: INDIVIDUAL NAME: ORION NEBULA (1)
- ISM: Individual: Name: Orion Nebula (1)
- ISM: PLANETARY NEBULAE: GENERAL (1)
- ISM: Planetary Nebulae: General (1)
- LINE: FORMATION (1)
- LINE: PROFILES (1)
- Line: Formation (1)
- Line: Profiles (1)
- MAGNETIC FIELDS (1)
- MASERS (1)
- Magnetic Fields (1)
- Masers (1)
- POLARIZATION (1)
- Polarization (1)
- RADIATIVE TRANSFER (1)
- Radiative Transfer (1)
Articles 1 - 5 of 5
Full-Text Articles in Physics
Quasars As Cosmological Probes: The Ionizing Continuum, Gas Metallicity, And The WΛ-L Relation, Kirk Korista, Jack Baldwin, Gary J. Ferland
Quasars As Cosmological Probes: The Ionizing Continuum, Gas Metallicity, And The WΛ-L Relation, Kirk Korista, Jack Baldwin, Gary J. Ferland
Physics and Astronomy Faculty Publications
Using a realistic model for line emission from the broad emission line regions of quasars, we are able to reproduce the previously observed correlations of emission-line ratios with the shape of the spectral energy distribution (SED). In agreement with previous studies, we find that the primary driving force behind the Baldwin effect (Wλ ~ Lβ, β < 0) is a global change in the SED with quasar luminosity, in that more luminous quasars must have characteristically softer ionizing continua. This is completely consistent with observations that show (1) a correlation between Luv, αox, and αuvx (2) correlations of SED shape-sensitive line ratios with αox, αuvx, and Luv; and (3) correlations between line equivalent widths and αox, αuvx …
Temperature Fluctuations In Photoionized Nebulae. Ii. The Effect Of Inhomogeneous Abundances, J. B. Kingdon, Gary J. Ferland
Temperature Fluctuations In Photoionized Nebulae. Ii. The Effect Of Inhomogeneous Abundances, J. B. Kingdon, Gary J. Ferland
Physics and Astronomy Faculty Publications
Recent abundance determinations based on recombination lines in several emission-line nebulae yield ionic abundances several times larger than those derived from forbidden lines. These results cast uncertainty over all abundance determinations in such objects. One possible explanation for these discrepancies frequently cited in the literature is the presence of chemical inhomogeneities. We have run a series of photoionization models to examine what effect such inhomogeneities will have on the resulting temperature structure of nebulae. We then derive abundances from these models, utilizing Peimbert's t2 formalism. Our results suggest that, although chemical inhomogeneities may produce nonnegligible biases in abundance determinations …
Polarization Of Astronomical Maser Radiation. Iv. Circular Polarization Profiles, Moshe Elitzur
Polarization Of Astronomical Maser Radiation. Iv. Circular Polarization Profiles, Moshe Elitzur
Physics and Astronomy Faculty Publications
Profile comparison of the Stokes parameters V and I is a powerful tool for maser data analysis, which provides the first direct methods for unambiguous determination of (1) the maser saturation stage, (2) the amplification optical depth and intrinsic Doppler width of unsaturated masers, and (3) the comparative magnitudes of Zeeman splitting and Doppler line width. Circular polarization recently detected in OH 1720 MHz emission from the Galactic center appears to provide the first direct evidence for maser saturation.
Temperature Variations And N/O In The Orion Nebula From Hst Observations, R. H. Rubin, P. G. Martin, R. J. Dufour, Gary J. Ferland, J. A. Baldwin, J. J. Hester, D. K. Walter
Temperature Variations And N/O In The Orion Nebula From Hst Observations, R. H. Rubin, P. G. Martin, R. J. Dufour, Gary J. Ferland, J. A. Baldwin, J. J. Hester, D. K. Walter
Physics and Astronomy Faculty Publications
Using the Goddard High Resolution Spectrograph (GHRS) and the Faint Object Spectrograph (FOS) on the Hubble Space Telescope, we measured the flux of the N II] (2s2p3 5S2 --> 2s22p2 3P2,1) lines at λvac = 2143.45, 2139.68 Å in the Orion Nebula--the first detection of these lines in an H II region. In order to assess the N+/O+ ratio, we also measured the flux of the [O II] (2p32Po1/2,3/2-->2p34So3/2) lines at λvac …
The Ultraviolet-Optical Albedo Of Broad Emission Line Clouds, Kirk Korista, Gary J. Ferland
The Ultraviolet-Optical Albedo Of Broad Emission Line Clouds, Kirk Korista, Gary J. Ferland
Physics and Astronomy Faculty Publications
We explore the effective UV-optical albedos of a variety of types of broad emission line clouds, as well as their possible effects on the observed spectra of active galactic nuclei (AGNs). An important albedo source in moderately ionized ionization-bounded clouds is that which is due to neutral hydrogen: Rayleigh scattering of continuum photons off the extreme damping wings of Lyα. The photons resulting from this scattering mechanism may contribute significantly to the Lyα emission line, especially in the very broad wings. In addition, line photons emitted near 1200 Å (e.g., N V λ1240) that stream toward the neutral portion of …