# Physics Commons™

Articles 1 - 30 of 221

## Full-Text Articles in Physics

Lanczos-Boosted Numerical Linked-Cluster Expansion For Quantum Lattice Models, Krishnakumar Bhattaram, Ehsan Khatami Jul 2019

#### Lanczos-Boosted Numerical Linked-Cluster Expansion For Quantum Lattice Models, Krishnakumar Bhattaram, Ehsan Khatami

##### Ehsan Khatami

Numerical linked-cluster expansions allow one to calculate finite-temperature properties of quantum lattice models directly in the thermodynamic limit through exact solutions of small clusters. However, full diagonalization is often the limiting factor for these calculations. Here we show that a partial diagonalization of the largest clusters in the expansion using the Lanczos algorithm can be as useful as full diagonalization for the method while mitigating some of the time and memory issues. As test cases, we consider the frustrated Heisenberg model on the checkerboard lattice and the Fermi-Hubbard model on the square lattice. We find that our approach can surpass ...

New Constraints On Early-Type Galaxy Assembly From Spectroscopic Metallicities Of Globular Clusters In M87, Alexa Villaume, Aaron J. Romanowsky, Jean Brodie, Jay Strader Jul 2019

#### New Constraints On Early-Type Galaxy Assembly From Spectroscopic Metallicities Of Globular Clusters In M87, Alexa Villaume, Aaron J. Romanowsky, Jean Brodie, Jay Strader

##### Aaron J. Romanowsky

The observed characteristics of globular cluster (GC) systems, such as metallicity distributions, are commonly used to place constraints on galaxy formation models. However, obtaining reliable metallicity values is particularly difficult because of our limited means to obtain high quality spectroscopy of extragalactic GCs. Often, "color–metallicity relations" are invoked to convert easier-to-obtain photometric measurements into metallicities, but there is no consensus on what form these relations should take. In this paper we make use of multiple photometric data sets and iron metallicity values derived from applying full-spectrum stellar population synthesis models to deep Keck/LRIS spectra of 177 GCs centrally ...

New Tests Of General Relativity, Quentin Bailey Jun 2019

#### New Tests Of General Relativity, Quentin Bailey

##### Quentin Bailey

The last decade has seen a rapid increase in the number of precision tests of relativity. This research has been motivated by the intriguing possibility that tiny deviations from relativity might arise in the underlying theory that is widely believed to successfully mesh General Relativity (GR) with quantum physics. Many of these tests have been analyzed within an effective field theory framework which generically describes possible deviations from exact relativity and contains some traditional test frameworks as limiting cases. One part of the activity has been a resurgence of interest in tests of relativity in the Minkowski-spacetime context, where Lorentz ...

Tests Of Lorentz Symmetry In The Gravitational Sector, Aurélien Hees, Quentin G. Bailey, Adrien Bourgoin, Hélène Pihan-Le Bars, Christine Guerlin, Christophe Le Poncin-Lafitte Jun 2019

#### Tests Of Lorentz Symmetry In The Gravitational Sector, Aurélien Hees, Quentin G. Bailey, Adrien Bourgoin, Hélène Pihan-Le Bars, Christine Guerlin, Christophe Le Poncin-Lafitte

##### Quentin Bailey

Lorentz symmetry is one of the pillars of both General Relativity and the Standard Model of particle physics. Motivated by ideas about quantum gravity, unification theories and violations of CPT symmetry, a significant effort has been put the last decades into testing Lorentz symmetry. This review focuses on Lorentz symmetry tests performed in the gravitational sector. We briefly review the basics of the pure gravitational sector of the Standard-Model Extension (SME) framework, a formalism developed in order to systematically parametrize hypothetical violations of the Lorentz invariance. Furthermore, we discuss the latest constraints obtained within this formalism including analyses of the ...

Prospects For Sme Tests With Experiments At Syrte And Lkb, C. Guerlin, H. Pihan-Le Bars, Q. G. Bailey, P. Wolf Jun 2019

#### Prospects For Sme Tests With Experiments At Syrte And Lkb, C. Guerlin, H. Pihan-Le Bars, Q. G. Bailey, P. Wolf

##### Quentin Bailey

Preliminary work has been done in order to assess the perspectives of metrology and fundamental physics atomic experiments at SYRTE and LKB in the search for physics beyond the Standard Model and General Relativity. The first studies we identified are currently ongoing with the Microscope mission and with a Cs fountain clock. The latter brings significant improvement on the proton-sector coefficient cTT down to the 10−17 GeV level.

Improved Tests Of Lorentz Invariance In The Matter Sector Using Atomic Clocks, H. Pihan-Le Bars, C. Guerlin, Q. G. Bailey, S. Bize, P. Wolf Jun 2019

#### Improved Tests Of Lorentz Invariance In The Matter Sector Using Atomic Clocks, H. Pihan-Le Bars, C. Guerlin, Q. G. Bailey, S. Bize, P. Wolf

##### Quentin Bailey

For the purpose of searching for Lorentz-invariance violation in the minimal Standard-Model Extension, we perfom a reanalysis of data obtained from the 133Cs fountain clock operating at SYRTE. The previous study led to new limits on eight components of the ˜cµν tensor, which quantifies the anisotropy of the proton’s kinetic energy. We recently derived an advanced model for the frequency shift of hyperfine Zeeman transition due to Lorentz violation and became able to constrain the ninth component, the isotropic coefficient c˜TT, which is the least well-constrained coefficient of ˜cµν. This model is based on a second-order boost Lorentz ...

Lorentz-Violating Electromagnetostatics, Quentin G. Bailey Jun 2019

#### Lorentz-Violating Electromagnetostatics, Quentin G. Bailey

##### Quentin Bailey

In this talk, the stationary limit of Lorentz-violating electrodynamics is discussed. As illustrated by some simple examples, the general solution includes unconventional mixing of electrostatic and magnetostatic effects. I discuss a high-sensitivity null-type measurement, exploiting Lorentz-violating electromagnetostatic effects, that could improve existing limits on parity-odd coefficients for Lorentz violation in the photon sector.

Gravity Sector Of The Sme, Q. G. Bailey Jun 2019

#### Gravity Sector Of The Sme, Q. G. Bailey

##### Quentin Bailey

In this talk, the gravity sector of the effective field theory description of local Lorentz violation is discussed, including minimal and nonminimal curvature couplings. Also, recent experimental and observational analyses including solar-system ephemeris and short-range gravity tests are reviewed.

Spatially Resolved Stellar Populations And Kinematics With Kcwi: Probing The Assembly History Of The Massive Early-Type Galaxy Ngc 1407, Anna Ferré-Mateu, Duncan A. Forbes, Richard M. Mcdermid, Aaron J. Romanowsky, Jean P. Brodie Jun 2019

#### Spatially Resolved Stellar Populations And Kinematics With Kcwi: Probing The Assembly History Of The Massive Early-Type Galaxy Ngc 1407, Anna Ferré-Mateu, Duncan A. Forbes, Richard M. Mcdermid, Aaron J. Romanowsky, Jean P. Brodie

##### Aaron J. Romanowsky

Using the newly commissioned Keck Cosmic Web Imager (KCWI) instrument on the Keck II telescope, we analyze the stellar kinematics and stellar populations of the well-studied massive early-type galaxy (ETG) NGC 1407. We obtained high signal-to-noise integral field spectra for a central and an outer (around one effective radius toward the southeast direction) pointing with integration times of just 600 s and 2400 s, respectively. We confirm the presence of a kinematically distinct core also revealed by VLT/MUSE data of the central regions. While NGC 1407 was previously found to have stellar populations characteristic of massive ETGs (with radially ...

Interpreting Particle Motion In Low-Gravity, Asteroidal Conditions With Image Processing And Analysis, Gillian Gomer, Adrienne Dove, Michael Fraser, Seamus Anderson, Kristen John, Marc Fries Mar 2019

#### Interpreting Particle Motion In Low-Gravity, Asteroidal Conditions With Image Processing And Analysis, Gillian Gomer, Adrienne Dove, Michael Fraser, Seamus Anderson, Kristen John, Marc Fries

##### Gillian Gomer

Asteroids and moons are small, atmosphereless bodies with dynamic surface activity that complicates image analysis and selection of future exploration sites. To better understand the distributions of surface material (regolith), the Strata-1 experiment utilized the microgravity, vibrational environment of the International Space Station (ISS) to replicate asteroidal conditions. Image data was collected, in which we observe both times of disruptive “events” and more passive “non-events” that cause small changes. The experiment contained several types of material to simulate asteroid surfaces. Here we analyze a single tube that contained aspherical glass shards. We have written a Python routine to split the ...

A Second Galaxy Missing Dark Matter In The Ngc 1052, Pieter Van Dokkum, Shany Danieli, Roberto Abraham, Charlie Conroy, Aaron J. Romanowsky Mar 2019

#### A Second Galaxy Missing Dark Matter In The Ngc 1052, Pieter Van Dokkum, Shany Danieli, Roberto Abraham, Charlie Conroy, Aaron J. Romanowsky

##### Aaron J. Romanowsky

The ultra-diffuse galaxy NGC1052-DF2 has a very low velocity dispersion, indicating that it has little or no dark matter. Here we report the discovery of a second galaxy in this class, residing in the same group. NGC1052-DF4 closely resembles NGC1052-DF2 in terms of its size, surface brightness, and morphology; has a similar distance of Dsbf =  19.9 2.8 Mpc; and also has a population of luminous globular clusters extending out to 7 kpc from the center of the galaxy. Accurate radial velocities of the diffuse galaxy light and seven of the globular clusters were obtained with the Low Resolution ...

Analysis Of Regolith Simulant Stratification And Migration In An Asteroid-Like Environment, Gillian Gomer, Michael Fraser, Adrienne Dove, Seamus Anderson, Akbar Whizin, Kristen John, Marc Fries Mar 2018

#### Analysis Of Regolith Simulant Stratification And Migration In An Asteroid-Like Environment, Gillian Gomer, Michael Fraser, Adrienne Dove, Seamus Anderson, Akbar Whizin, Kristen John, Marc Fries

##### Gillian Gomer

No abstract provided.

Hypervolatiles In A Jupiter-Family Comet: Observations Of 45p/Honda–Mrkos–Pajdušáková Using Ishell At The Nasa-Irtf, Michael A. Disanti, Boncho P. Bonev, Neil Dello Russo, Ronald J. Vervack, Erika L. Gibb, Nathan X. Roth, Adam J. Mckay, Hideyo Kawakita, Lori M. Feaga, Harold A. Weaver Nov 2017

#### Hypervolatiles In A Jupiter-Family Comet: Observations Of 45p/Honda–Mrkos–Pajdušáková Using Ishell At The Nasa-Irtf, Michael A. Disanti, Boncho P. Bonev, Neil Dello Russo, Ronald J. Vervack, Erika L. Gibb, Nathan X. Roth, Adam J. Mckay, Hideyo Kawakita, Lori M. Feaga, Harold A. Weaver

##### Erika Gibb

We used the new high spectral resolution cross-dispersed facility spectrograph, iSHELL, at the NASA Infrared Telescope Facility on Maunakea, HI, to observe Jupiter-family comet (JFC) 45P/Honda–Mrkos–Pajdušáková. We report water production rates, as well as production rates and abundance ratios relative to H2O, for eight trace parent molecules (native ices), CO, CH4, H2CO, CH3OH, HCN, NH3, C2H2, and C2H6, on 2 days spanning UT 2017 January 6/7 and 7/8, shortly following perihelion. Trace species were measured simultaneously with H2O and/or OH prompt emission, a proxy for H2O production, thereby providing a robust and consistent means ...

"Blinded By The Lines: Mid-Ir Spectra Of Mira Variables Taken With Spitzer", Dana Baylis-Aguirre, Michelle J. Creech-Eakman, Donald G. Luttermoser, Tina Gueth Aug 2017

#### "Blinded By The Lines: Mid-Ir Spectra Of Mira Variables Taken With Spitzer", Dana Baylis-Aguirre, Michelle J. Creech-Eakman, Donald G. Luttermoser, Tina Gueth

##### Donald G. Luttermoser

We present preliminary analysis of mid-infrared spectra of M-type and C-type Mira variables. Due to the brightness of this sample, it is straightforward to monitor changes with phase in the infrared spectral features of these regular pulsators. We have spectra of 25 Mira variables, taken with phase, using the Spitzer Infrared Spectrograph (IRS) high-resolution module. Each star has multiple spectra obtained over a one-year period from 2008-09. This is a rich, unique data set due to multiple observations of each star and the high signal-to-noise ratio from quick exposure times to prevent saturation of the IRS instrument. This paper focuses ...

May 2017

Gravitational-waves, as predicted by Einstein’s theory of general relativity, are oscillations of spacetime caused by the motion of masses. Although not yet directly detected, there is strong evidence for the existence of gravitational-waves. Detectable gravitational waves will come from dramatic astrophysical events, such as supernova explosions and collisions of black holes. The Laser Interferometer Gravitational-wave Observatory (LIGO) is a network of detectors designed to make the first direct detection of gravitational waves. The upgraded version of LIGO, Advanced LIGO (aLIGO), will offer a dramatic improvement in sensitivity that will virtually guarantee detections. Gravitational-wave detections will not only illuminate mysterious ...

May 2017

#### Gravitational Waves From Rotating Neutron Stars And Compact Binary Systems, Leslie Wade

It is widely anticipated that the first direct detections of gravitational waves will be made by advanced gravitational-wave detectors, such as the two Laser Interferometer Gravitational-wave Observatories (LIGO) and the Virgo interferometer. In preparation for the advanced detector era, I have worked on both detection and post-detection efforts involving two gravitational wave sources: isolated rotating neutron stars (NSs) and compact binary coalescences (CBCs). My dissertation includes three main research projects: 1) a population synthesis study assessing the detectability of isolated NSs, 2) a CBC search for intermediate-mass black-hole binaries (IMBHBs), and 3) new methods for directly measuring the neutron-star (NS ...

Beyond 3 Au From The Sun: The Hypervolatiles Ch4, C2h6, And Co In The Distant Comet C/2006 W3 (Christensen), Boncho P. Bonev, Geronimo L. Villanueva, Michael A. Disanti, Hermann Boehnhardt, Manuela Lippi, Erika L. Gibb, Lucas Paganini, Michael J. Mumma May 2017

#### Beyond 3 Au From The Sun: The Hypervolatiles Ch4, C2h6, And Co In The Distant Comet C/2006 W3 (Christensen), Boncho P. Bonev, Geronimo L. Villanueva, Michael A. Disanti, Hermann Boehnhardt, Manuela Lippi, Erika L. Gibb, Lucas Paganini, Michael J. Mumma

##### Erika Gibb

Comet C/2006 W3 (Christensen) remained outside a heliocentric distance (R h) of 3.1 au throughout its apparition, but it presented an exceptional opportunity to directly sense a suite of molecules released from its nucleus. The Cryogenic Infrared Echelle Spectrograph at ESO-VLT detected infrared emissions from the three "hypervolatiles" (CO, CH4, and C2H6) that have the lowest sublimation temperatures among species that are commonly studied in comets by remote sensing. Even at R h = 3.25 au, the production rate of each molecule exceeded those measured for the same species in a number of other comets, although these comets ...

The Composition Of Comet C/2012 K1 (Panstarrs) And The Distribution Of Primary Volatile Abundances Among Comets, Nathan X. Roth, Erika L. Gibb, Boncho P. Bonev, Michael A. Disanti, Michael J. Mumma, Geronimo L. Villanueva, Lucas Paganini Mar 2017

#### The Composition Of Comet C/2012 K1 (Panstarrs) And The Distribution Of Primary Volatile Abundances Among Comets, Nathan X. Roth, Erika L. Gibb, Boncho P. Bonev, Michael A. Disanti, Michael J. Mumma, Geronimo L. Villanueva, Lucas Paganini

##### Erika Gibb

On 2014 May 22 and 24 we characterized the volatile composition of the dynamically new Oort cloud comet C/2012 K1 (PanSTARRS) using the long-slit, high resolution (λ/Δλ ≈ 25,000) near-infrared echelle spectrograph (NIRSPEC) at the 10 m Keck II telescope on Maunakea, Hawaii. We detected fluorescent emission from six primary volatiles (H2O, HCN, CH4, C2H6, CH3OH, and CO). Upper limits were derived for C2H2, NH3, and H2CO. We report rotational temperatures, production rates, and mixing ratios (relative to water). Compared with median abundance ratios for primary volatiles in other sampled Oort cloud comets, trace gas abundance ratios in ...

Thermal Plasmaspheric Morphology: Effect Of Geomagnetic And Solar Activity, Mark Anthony Reynolds, G. Ganguli, J.A. Fedder, J. Lemaire, R.R. Meier, D.J. Melendez-Alvira Mar 2017

#### Thermal Plasmaspheric Morphology: Effect Of Geomagnetic And Solar Activity, Mark Anthony Reynolds, G. Ganguli, J.A. Fedder, J. Lemaire, R.R. Meier, D.J. Melendez-Alvira

##### M. Anthony Reynolds

A multispecies kinetic model of the thermal plasma in the plasmasphere is used to predict the spatial dependence of the hydrogen ion and helium ion density and temperature for different levels of geomagnetic and solar activity. The particular convection electric field model chosen is intended for the time intervals between substorms. The plasma density and temperature in the equatorial plane are found to exhibit a local-time variation that is sensitive to the details of the convection electric field. In particular, the parallel temperature increases with altitude and the perpendicular temperature decreases with altitude, except in the postmidnight sector, features that ...

Measurement Of The Stochasticity Of Low-Latitude Geomagnetic Temporal Variations, Mark Anthony Reynolds, James A. Wanliss Mar 2017

#### Measurement Of The Stochasticity Of Low-Latitude Geomagnetic Temporal Variations, Mark Anthony Reynolds, James A. Wanliss

##### M. Anthony Reynolds

Ground magnetometer measurements of total magnetic field strength from 6 stations at low latitudes were analyzed using power spectrum and Hurst range scaling techniques. The Hurst exponents for most of these time-series were near 0.5, which indicates stochasticity, with the highest latitude stations exhibiting some persistence with Hurst exponents greater than 0.6. Although no definite correlations are evident, the relative increase of the Hurst exponent with latitude suggests the possibility that the underlying dynamics of the magnetosphere change with latitude. This result may help quantify the dynamics of the inner magnetosphere itself without the direct presence of the ...

Inversion Of Plasmaspheric Euv Remote Sensing Data From The Stp 72-1 Satellite, R.R. Meier, A.C. Nicholas, J.M. Picone, D.J. Melendez-Alvira, G. Ganguli, Mark Anthony Reynolds, E.C. Roelof Mar 2017

#### Inversion Of Plasmaspheric Euv Remote Sensing Data From The Stp 72-1 Satellite, R.R. Meier, A.C. Nicholas, J.M. Picone, D.J. Melendez-Alvira, G. Ganguli, Mark Anthony Reynolds, E.C. Roelof

##### M. Anthony Reynolds

Observations of the extreme ultraviolet emission of helium ions at 30.4 nm can be used to study the global shape of the plasmasphere and its dynamical response to geomagnetic forcing. In order to retrieve number densities of plasmaspheric He+ from such observations, we have developed a new inversion technique based on discrete inverse theory, which uses the optical data to optimize a parameterized model of the He+ distribution. We apply this inversion technique to several orbits of data obtained from the Naval Research Laboratory extreme ultraviolet photometric experiment launched on the STP 72-1 satellite in October 1972. The inversion ...

Exotic Statistics For Strings In 4d Bf Theory, John C. Baez, Derek K. Wise, Alissa S. Crans Dec 2016

#### Exotic Statistics For Strings In 4d Bf Theory, John C. Baez, Derek K. Wise, Alissa S. Crans

##### Alissa Crans

After a review of exotic statistics for point particles in 3d BF theory, and especially 3d quantum gravity, we show that string-like defects in 4d BF theory obey exotic statistics governed by the 'loop braid group'. This group has a set of generators that switch two strings just as one would normally switch point particles, but also a set of generators that switch two strings by passing one through the other. The first set generates a copy of the symmetric group, while the second generates a copy of the braid group. Thanks to recent work of Xiao-Song Lin, we can ...

En Route To Destruction: The Evolution In Composition Of Ices In Comet D/2012 S1 (Ison) Between 1.2 And 0.34 Au From The Sun As Revealed At Infrared Wavelengths, M. A. Disanti, B. P. Bonev, E. L. Gibb, L. Paganini, G. L. Villanueva, M. J. Mumma, J. V. Keane, G. A. Blake, N. Dello Russo, K. J. Meech, R. J. Vervack, A. J. Mckay Mar 2016

#### En Route To Destruction: The Evolution In Composition Of Ices In Comet D/2012 S1 (Ison) Between 1.2 And 0.34 Au From The Sun As Revealed At Infrared Wavelengths, M. A. Disanti, B. P. Bonev, E. L. Gibb, L. Paganini, G. L. Villanueva, M. J. Mumma, J. V. Keane, G. A. Blake, N. Dello Russo, K. J. Meech, R. J. Vervack, A. J. Mckay

##### Erika Gibb

We report production rates for H2O and eight trace molecules (CO, C2H6, CH4, CH3OH, NH3, H2CO, HCN, C2H2) in the dynamically new, Sun-grazing Comet C/2012 S1 (ISON), using high-resolution spectroscopy at Keck II and the NASA IRTF on 10 pre-perihelion dates encompassing heliocentric distances Rh = 1.21–0.34 AU. Measured water production rates spanned two orders of magnitude, consistent with a long-term heliocentric power law Q(H2O) ${\rm{\propto }}{R}_{{\rm{h}}}^{(-3.1\pm 0.1)}$. Abundance ratios for CO, C2H6, and CH4 with respect to H2O remained constant with Rh and below their corresponding mean ...

Holographic Renormalization Of Asymptotically Lifshitz Spacetimes, Robert Mcnees, Robert Mann Jan 2016

#### Holographic Renormalization Of Asymptotically Lifshitz Spacetimes, Robert Mcnees, Robert Mann

##### Robert A McNees IV

A variational formulation is given for a theory of gravity coupled to a massive vector in four dimensions, with Asymptotically Lifshitz boundary conditions on the fields. For theories with critical exponent z=2 we obtain a well-defined variational principle by explicitly constructing two actions with local boundary counterterms. As part of our analysis we obtain solutions of these theories on a neighborhood of spatial infinity, study the asymptotic symmetries, and consider different definitions of the boundary stress tensor and associated charges. A constraint on the boundary data for the fields figures prominently in one of our formulations, and in that ...

Black Holes In The Conical Ensemble, Robert Mcnees, Daniel Grumiller Jan 2016

#### Black Holes In The Conical Ensemble, Robert Mcnees, Daniel Grumiller

##### Robert A McNees IV

We consider black holes in an “unsuitable box”: a finite cavity coupled to a thermal reservoir at a temperature different than the black hole’s Hawking temperature. These black holes are described by metrics that are continuous but not differentiable due to a conical singularity at the horizon. We include them in the Euclidean path integral sum over configurations, and analyze the effect this has on black hole thermodynamics in the canonical ensemble. Black holes with a small deficit (or surplus) angle may have a smaller internal energy or larger density of states than the nearby smooth black hole, but ...

Jan 2016

#### Conventions, Definitions, Identities, And Other Useful Formulae, Robert Mcnees

##### Robert A McNees IV

As the name suggests, these notes contain a summary of important conventions, definitions, identities, and various formulas that I often refer to. They may prove useful for researchers working in General Relativity, Supergravity, String Theory, Cosmology, and related areas.

Boundary Terms Unbound! Holographic Renormalization Of Asymptotically Linear Dilaton Gravity, Robert Mcnees, Robert Mann Jan 2016

#### Boundary Terms Unbound! Holographic Renormalization Of Asymptotically Linear Dilaton Gravity, Robert Mcnees, Robert Mann

##### Robert A McNees IV

A variational principle is constructed for gravity coupled to an asymptotically linear dilaton and a p-form field strength. This requires the introduction of appropriate surface terms—also known as 'boundary counterterms'—in the action. The variation of the action with respect to the boundary metric yields a boundary stress tensor, which is used to construct conserved charges that generate the asymptotic symmetries of the theory. In most cases a minimal set of assumptions leads to a unique set of counterterms. However, for certain examples we find families of actions that depend on one or more continuous parameters. We show that ...

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 Oct 2015

#### 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

##### Gary J. Ferland

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 = 2471.05, 2471.12 Å. In addition, with the FOS, other emission lines were measured in the same aperture in order ...

High Metal Enrichments In Luminous Quasars, Gary J. Ferland, Jack A. Baldwin, Kirk T. Korista, Fred Hamann, R. F. Carswell, Mark Phillips, Belinda J. Wilkes, Robert E. Williams Oct 2015

#### High Metal Enrichments In Luminous Quasars, Gary J. Ferland, Jack A. Baldwin, Kirk T. Korista, Fred Hamann, R. F. Carswell, Mark Phillips, Belinda J. Wilkes, Robert E. Williams

##### Gary J. Ferland

We discuss observations of the broad emission line in luminous intermediate redshift quasars, with emphasis on Q0207 -398. This object has relatively sharp lines, allowing us to deconvolve the profiles into distinct components. In this paper we examine the high ionization region, which we show must be matter-bounded, partially transparent to ionizing radiation. We measure a large N V λ1240/He II λ1640 ratio in Q0207-398, but detailed calculations predict this ratio to be ~1 for standard cloud properties. We show that no choice of incident continuum, ionizing photon flux, density, or even the appeal to nonradiative energy sources, can ...

Optically Thin Broad-Line Clouds In Active Galactic Nuclei, Joseph C. Shields, Gary J. Ferland, Bradley M. Peterson Oct 2015

#### Optically Thin Broad-Line Clouds In Active Galactic Nuclei, Joseph C. Shields, Gary J. Ferland, Bradley M. Peterson

##### Gary J. Ferland

The broad-line region (BLR) in Seyfert galaxy nuclei exhibits correlated variations in continuum and emission-line luminosity that are qualitatively consistent with photoionization of ionization-bounded (optically thick) clouds. However, evidence is growing that a nonnegligible fraction of the BLR cloud population is optically thin to the Lyman continuum and fully ionized in hydrogen. We consider the implications of this nebular component for observed line emission and find that inclusion of thin clouds in photoionization calculations can resolve several outstanding puzzles of Seyfert variability, notably the behavior of the C IV λ1549/Lyα ratio as a function of continuum luminosity. A similar ...