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- Active galaxies (4)
- Galaxy nuclei (4)
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- Galaxies: clusters: individual: Perseus (1)
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Articles 1 - 19 of 19
Full-Text Articles in Physics
Testing Diagnostics Of Nuclear Activity And Star Formation In Galaxies At Z > 1, Jonathan R. Trump, Nicholas P. Konidaris, Guillermo Barro, David C. Koo, Dale D. Kocevski, Stéphanie Juneau, Benjamin J. Weiner, S. M. Faber, Ian S. Mclean, Renbin Yan, Pablo G. Pérez-González, Victor Villar
Testing Diagnostics Of Nuclear Activity And Star Formation In Galaxies At Z > 1, Jonathan R. Trump, Nicholas P. Konidaris, Guillermo Barro, David C. Koo, Dale D. Kocevski, Stéphanie Juneau, Benjamin J. Weiner, S. M. Faber, Ian S. Mclean, Renbin Yan, Pablo G. Pérez-González, Victor Villar
Physics and Astronomy Faculty Publications
We present some of the first science data with the new Keck/MOSFIRE instrument to test the effectiveness of different AGN/SF diagnostics at z ~ 1.5. MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S field, resulting in 2 hr exposures of 36 emission-line galaxies. We compare X-ray data with the traditional emission-line ratio diagnostics and the alternative mass-excitation and color-excitation diagrams, combining new MOSFIRE infrared data with previous HST/WFC3 infrared spectra (from the 3D-HST survey) and multiwavelength photometry. We demonstrate that a high [O III]/Hβ ratio is insufficient as an active galactic nucleus (AGN) indicator …
The Central Molecular Gas Structure In Liners With Low-Luminosity Active Galactic Nuclei: Evidence For Gradual Disappearance Of The Torus, F. Müller-Sánchez, M. A. Prieto, M. Mezcua, R. I. Davies, M. A. Malkan, Moshe Elitzur
The Central Molecular Gas Structure In Liners With Low-Luminosity Active Galactic Nuclei: Evidence For Gradual Disappearance Of The Torus, F. Müller-Sánchez, M. A. Prieto, M. Mezcua, R. I. Davies, M. A. Malkan, Moshe Elitzur
Physics and Astronomy Faculty Publications
We present observations of the molecular gas in the nuclear environment of three prototypical low-luminosity active galactic nuclei (LLAGNs), based on VLT/SINFONI AO-assisted integral-field spectroscopy of H2 1-0 S(1) emission at angular resolutions of ~0.''17. On scales of 50-150 pc, the spatial distribution and kinematics of the molecular gas are consistent with a rotating thin disk, where the ratio of rotation (V) to dispersion (σ) exceeds unity. However, in the central 50 pc, the observations reveal a geometrically and optically thick structure of molecular gas (V/σ < 1 and N H > 1023 cm–2 …
Two-Component Structure Of The HΒ Broad-Line Region In Quasars. I. Evidence From Spectral Principal Component Analysis, Chen Hu, Jian-Min Wang, Luis C. Ho, Gary J. Ferland, Jack A. Baldwin, Ye Wang
Two-Component Structure Of The HΒ Broad-Line Region In Quasars. I. Evidence From Spectral Principal Component Analysis, Chen Hu, Jian-Min Wang, Luis C. Ho, Gary J. Ferland, Jack A. Baldwin, Ye Wang
Physics and Astronomy Faculty Publications
We report on a spectral principal component analysis (SPCA) of a sample of 816 quasars, selected to have small Fe II velocity shifts with spectral coverage in the rest wavelength range 3500-5500 Å. The sample is explicitly designed to mitigate spurious effects on SPCA induced by Fe II velocity shifts. We improve the algorithm of SPCA in the literature and introduce a new quantity, the fractional-contribution spectrum, that effectively identifies the emission features encoded in each eigenspectrum. The first eigenspectrum clearly records the power-law continuum and very broad Balmer emission lines. Narrow emission lines dominate the second eigenspectrum. The …
Pumping Up The [N I] Nebular Lines, Gary J. Ferland, W. J. Henney, C. R. O'Dell, R. L. Porter, P. A. M. Vanhoof, R. J. R. Williams
Pumping Up The [N I] Nebular Lines, Gary J. Ferland, W. J. Henney, C. R. O'Dell, R. L. Porter, P. A. M. Vanhoof, R. J. R. Williams
Physics and Astronomy Faculty Publications
The optical [N I] doublet near 5200 Å is anomalously strong in a variety of emission-line objects. We compute a detailed photoionization model and use it to show that pumping by far-ultraviolet (FUV) stellar radiation previously posited as a general explanation applies to the Orion Nebula (M42) and its companion M43; but, it is unlikely to explain planetary nebulae and supernova remnants. Our models establish that the observed nearly constant equivalent width of [N I] with respect to the dust-scattered stellar continuum depends primarily on three factors: the FUV to visual-band flux ratio of the stellar population, the optical properties …
Improved He I Emissivities In The Case B Approximation, R. L. Porter, Gary J. Ferland, P. J. Storey, M. J. Detisch
Improved He I Emissivities In The Case B Approximation, R. L. Porter, Gary J. Ferland, P. J. Storey, M. J. Detisch
Physics and Astronomy Faculty Publications
We update our prior work on the case B collisional-recombination spectrum of He i to incorporate ab initio photoionization cross-sections. This large set of accurate, self-consistent cross-sections represents a significant improvement in He i emissivity calculations because it largely obviates the piecemeal nature that has marked all modern works. A second, more recent set of ab initio cross-sections is also available, but we show that those are less consistent with bound-bound transition probabilities than our adopted set. We compare our new effective recombination coefficients with our prior work and our new emissivities with those by other researchers, and we conclude …
Residual Cooling And Persistent Star Formation Amid Active Galactic Nucleus Feedback In Abell 2597, G. R. Tremblay, C. P. O'Dea, S. A. Baum, T. E. Clarke, C. L. Sarazin, J. N. Bregman, F. Combes, M. Donahue, A. C. Edge, A. C. Fabian, Gary J. Ferland, B. R. Mcnamara, R. Mittal, J. B. R. Oonk, A. C. Quillen, H. R. Russell, J. S. Sanders, P. Salomé, G. M. Voit, R. J. Wilman, M. W. Wise
Residual Cooling And Persistent Star Formation Amid Active Galactic Nucleus Feedback In Abell 2597, G. R. Tremblay, C. P. O'Dea, S. A. Baum, T. E. Clarke, C. L. Sarazin, J. N. Bregman, F. Combes, M. Donahue, A. C. Edge, A. C. Fabian, Gary J. Ferland, B. R. Mcnamara, R. Mittal, J. B. R. Oonk, A. C. Quillen, H. R. Russell, J. S. Sanders, P. Salomé, G. M. Voit, R. J. Wilman, M. W. Wise
Physics and Astronomy Faculty Publications
New Chandra X-ray and Herschel Far-Infrared (FIR) observations enable a multiwavelength study of active galactic nucleus (AGN) heating and intracluster medium (ICM) cooling in the brightest cluster galaxy (BCG) of Abell 2597 (z= 0.0821). The new Chandra observations reveal the central ≲30 kpc X-ray cavity network to be more extensive than previously thought, and associated with enough enthalpy to theoretically inhibit the inferred classical cooling flow. Nevertheless, we present new evidence, consistent with previous results, that a moderately strong residual cooling flow is persisting at 4–8 per cent of the classically predicted rates in a spatially structured manner …
The Nuclear Infrared Emission Of Low-Luminosity Active Galactic Nuclei, R. E. Mason, E. Lopez-Rodriguez, C. Packham, A. Alonso-Herrero, N. A. Levenson, J. Radomski, C. Ramos Almeida, L. Colina, Moshe Elitzur, I. Aretxaga, P. F. Roche, N. Oi
The Nuclear Infrared Emission Of Low-Luminosity Active Galactic Nuclei, R. E. Mason, E. Lopez-Rodriguez, C. Packham, A. Alonso-Herrero, N. A. Levenson, J. Radomski, C. Ramos Almeida, L. Colina, Moshe Elitzur, I. Aretxaga, P. F. Roche, N. Oi
Physics and Astronomy Faculty Publications
We present high-resolution mid-infrared (MIR) imaging, nuclear spectral energy distributions (SEDs), and archival Spitzer spectra for 22 low-luminosity active galactic nuclei (LLAGNs; Lbol ≲ 1042 erg s–1). Infrared (IR) observations may advance our understanding of the accretion flows in LLAGNs, the fate of the obscuring torus at low accretion rates, and, perhaps, the star formation histories of these objects. However, while comprehensively studied in higher-luminosity Seyferts and quasars, the nuclear IR properties of LLAGNs have not yet been well determined. We separate the present LLAGN sample into three categories depending on their Eddington ratio and radio …
The Curious Conundrum Regarding Sulfur Abundances In Planetary Nebulae, R. B. C. Henry, Angela Speck, Amanda I. Karakas, Gary J. Ferland, Mason Maguire
The Curious Conundrum Regarding Sulfur Abundances In Planetary Nebulae, R. B. C. Henry, Angela Speck, Amanda I. Karakas, Gary J. Ferland, Mason Maguire
Physics and Astronomy Faculty Publications
Sulfur abundances derived from optical emission line measurements and ionization correction factors (ICFs) in planetary nebulae are systematically lower than expected for the objects' metallicities. We have carefully considered a large range of explanations for this "sulfur anomaly," including: (1) correlations between the size of the sulfur deficit and numerous nebular and central star properties, (2) ICFs which undercorrect for unobserved ions, (3) effects of dielectronic recombination on the sulfur ionization balance, (4) sequestering of S into dust and/or molecules, and (5) excessive destruction of S or production of O by asymptotic giant branch stars. It appears that all but …
Ion-By-Ion Cooling Efficiencies, Orly Gnat, Gary J. Ferland
Ion-By-Ion Cooling Efficiencies, Orly Gnat, Gary J. Ferland
Physics and Astronomy Faculty Publications
We present ion-by-ion cooling efficiencies for low-density gas. We use Cloudy (version 10.00) to estimate the cooling efficiencies for each ion of the first 30 elements (H-Zn) individually. We present results for gas temperatures between 104 and 108 K, assuming low densities and optically thin conditions. When nonequilibrium ionization plays a significant role the ionization states deviate from those that obtain in collisional ionization equilibrium (CIE), and the local cooling efficiency at any given temperature depends on specific nonequilibrium ion fractions. The results presented here allow for an efficient estimate of the total cooling efficiency for any ionic …
On The Unification Of Active Galactic Nuclei, Moshe Elitzur
On The Unification Of Active Galactic Nuclei, Moshe Elitzur
Physics and Astronomy Faculty Publications
The inevitable spread in properties of the toroidal obscuration of active galactic nuclei (AGNs) invalidates the widespread notion that type 1 and 2 AGNs are intrinsically the same objects, drawn randomly from the distribution of torus covering factors. Instead, AGNs are drawn preferentially from the distribution; type 2 are more likely drawn from the distribution higher end, type 1 from its lower end. Type 2 AGNs have a higher IR luminosity, lower narrow-line luminosity, and a higher fraction of Compton thick X-ray obscuration than type 1. Meaningful studies of unification statistics cannot be conducted without first determining the intrinsic distribution …
Star Formation In Self-Gravitating Disks In Active Galactic Nuclei. Ii. Episodic Formation Of Broad-Line Regions, Jian-Min Wang, Pu Du, Jack A. Baldwin, Jun-Qiang Ge, Chen Hu, Gary J. Ferland
Star Formation In Self-Gravitating Disks In Active Galactic Nuclei. Ii. Episodic Formation Of Broad-Line Regions, Jian-Min Wang, Pu Du, Jack A. Baldwin, Jun-Qiang Ge, Chen Hu, Gary J. Ferland
Physics and Astronomy Faculty Publications
This is the second in a series of papers discussing the process and effects of star formation in the self-gravitating disk around the supermassive black holes in active galactic nuclei (AGNs). We have previously suggested that warm skins are formed above the star-forming (SF) disk through the diffusion of warm gas driven by supernova explosions. Here we study the evolution of the warm skins when they are exposed to the powerful radiation from the inner part of the accretion disk. The skins initially are heated to the Compton temperature, forming a Compton atmosphere (CAS) whose subsequent evolution is divided into …
Rovibrationally Resolved Direct Photodissociation Through The Lyman And Werner Transitions Of H2 For Fuv/X-Ray-Irradiated Environments, C. D. Gay, N. P. Abel, R. L. Porter, P. C. Stancil, Gary J. Ferland, G. Shaw, P. A. M. Vanhoof, R. J. R. Williams
Rovibrationally Resolved Direct Photodissociation Through The Lyman And Werner Transitions Of H2 For Fuv/X-Ray-Irradiated Environments, C. D. Gay, N. P. Abel, R. L. Porter, P. C. Stancil, Gary J. Ferland, G. Shaw, P. A. M. Vanhoof, R. J. R. Williams
Physics and Astronomy Faculty Publications
Using ab initio potential curves and dipole transition moments, cross-section calculations were performed for the direct continuum photodissociation of H2 through the B1Σ+u ← X1Σ+g (Lyman) and C1Πu ← X1Σ+g (Werner) transitions. Partial cross-sections were obtained for wavelengths from 100 Å to the dissociation threshold between the upper electronic state and each of the 301 bound rovibrational levels v''J'' within the ground electronic state. The resulting cross-sections are incorporated into three representative classes of interstellar gas models: diffuse clouds, photon-dominated regions, and …
Near Infrared Hydrogen Emission Line Ratios As Diagnostics Of The Broad Emission Line Region, Andrea J. Ruff, David J. E. Floyd, Kirk T. Korista, Rachel L. Webster, Ryan Lucian Porter, Gary J. Ferland
Near Infrared Hydrogen Emission Line Ratios As Diagnostics Of The Broad Emission Line Region, Andrea J. Ruff, David J. E. Floyd, Kirk T. Korista, Rachel L. Webster, Ryan Lucian Porter, Gary J. Ferland
Physics and Astronomy Faculty Publications
Broad emission line flux ratios are a powerful diagnostic of the physical conditions of the broad-line region gas in Active Galactic Nuclei. With recent advances in infrared spectroscopy, previously unstudied emission lines provide a new means to investigate the physical nature of the BELR gas. The hydrogen emission lines are particularly sensitive to the upper limits of both the radius from the central ionising source and the number density of the gas. Using an existing subset of near-infrared quasar spectra from the Glikman et al. (2006) sample [1] together with Cloudy photoionization simulations, we confirm the Locally Optimally emitting Cloud …
Herschel Observations Of Extended Atomic Gas In The Core Of The Perseus Cluster, R. Mittal, J. B. R. Oonk, Gary J. Ferland, A. C. Edge, C. P. O'Dea, S. A. Baum, J. T. Whelan, R. M. Johnstone, F. Combes, P. Salomé, A. C. Fabian, G. R. Tremblay, M. Donahue, Russell H. H.
Herschel Observations Of Extended Atomic Gas In The Core Of The Perseus Cluster, R. Mittal, J. B. R. Oonk, Gary J. Ferland, A. C. Edge, C. P. O'Dea, S. A. Baum, J. T. Whelan, R. M. Johnstone, F. Combes, P. Salomé, A. C. Fabian, G. R. Tremblay, M. Donahue, Russell H. H.
Physics and Astronomy Faculty Publications
We present Herschel observations of the core of the Perseus cluster of galaxies. Especially intriguing is the network of filaments that surround the brightest cluster galaxy, NGC 1275, previously imaged extensively in Hα and CO. In this work, we report detections of far-infrared (FIR) lines, in particular, [C II] 158, [O I] 63, [N II] 122, [O IB] 145 and [O III] 88 μm, withHerschel. All lines are spatially extended, except [O III], with the [C II] line emission extending up to 25 kpc from the core. [C II] emission is found to be co-spatial with Hα and …
Hydrogen Two-Photon Continuum Emission From The Horseshoe Filament In Ngc 1275, R. M. Johnstone, R. E.A. Canning, A. C. Fabian, Gary J. Ferland, Matt Lykins, R. L. Porter, P. A.M. Vanhoof, R. J.R. Williams
Hydrogen Two-Photon Continuum Emission From The Horseshoe Filament In Ngc 1275, R. M. Johnstone, R. E.A. Canning, A. C. Fabian, Gary J. Ferland, Matt Lykins, R. L. Porter, P. A.M. Vanhoof, R. J.R. Williams
Physics and Astronomy Faculty Publications
Far-ultraviolet emission has been detected from a knot of Hα emission in the Horseshoe filament, far out in the NGC 1275 nebula. The flux detected relative to the brightness of the Hα line in the same spatial region is very close to that expected from hydrogen two-photon continuum emission in the particle heating model of Ferland et al. if reddening internal to the filaments is taken into account. We find no need to invoke other sources of far-ultraviolet emission such as hot stars or emission lines from C IV in intermediate-temperature gas to explain these data.
The Influence Of Soft Spectral Components On The Structure And Stability Of Warm Absorbers In Active Galactic Nuclei, Susmita Chakravorty, Ranjeev Misra, Martin Elvis, Ajit K. Kembhavi, Gary J. Ferland
The Influence Of Soft Spectral Components On The Structure And Stability Of Warm Absorbers In Active Galactic Nuclei, Susmita Chakravorty, Ranjeev Misra, Martin Elvis, Ajit K. Kembhavi, Gary J. Ferland
Physics and Astronomy Faculty Publications
The radiation from the central regions of active galactic nuclei, including that from the accretion disc surrounding the black hole, is likely to peak in the extreme-ultraviolet ∼13–100 eV. However, due to Galactic absorption, we are limited to constrain the physical properties, i.e. the black hole mass and the accretion rate, from what observations we have below ∼10 eV or above ∼100 eV. In this paper, we predict the thermal and ionization states of warm absorbers as a function of the shape of the unobservable continuum. In particular we model an accretion disc at kTin∼ 10 eV and …
Intervening Broad-Line Region Clouds' Effects On The Optical/Ultraviolet Spectrum, Ye Wang, Gary J. Ferland, Chen Hu, Jian-Min Wang, Pu Du
Intervening Broad-Line Region Clouds' Effects On The Optical/Ultraviolet Spectrum, Ye Wang, Gary J. Ferland, Chen Hu, Jian-Min Wang, Pu Du
Physics and Astronomy Faculty Publications
Recent X-ray observations of Mrk 766 suggest that broad emission-line region clouds cross our line of sight and produce variable X-ray absorption. Here we investigate what optical/ultraviolet (UV) spectroscopic features would be produced by such ‘intervening broad-line region (BLR) clouds' (IBC) crossing our line of sight to the accretion disc, the source of the optical/UV continuum. Although the emission spectrum produced by intervening clouds is identical to the standard BLR model, they may produce absorption features on the optical or UV continuum. Single clouds will have little effect on the optical/UV spectrum because BLR clouds are likely to be much …
Multiphase Signatures Of Active Galactic Nucleus Feedback In Abell 2597, G. R. Tremblay, C. P. O'Dea, S. A. Baum, T. E. Clarke, C. L. Sarazin, J. N. Bregman, F. Combes, M. Donahue, A. C. Edge, A. C. Fabian, Gary J. Ferland, B. R. Mcnamara, R. Mittal, J. B. R. Oonk, A. C. Quillen, H. R. Russell, J. S. Sanders, P. Salomé, G. M. Voit, R. J. Wilman, M. W. Wise
Multiphase Signatures Of Active Galactic Nucleus Feedback In Abell 2597, G. R. Tremblay, C. P. O'Dea, S. A. Baum, T. E. Clarke, C. L. Sarazin, J. N. Bregman, F. Combes, M. Donahue, A. C. Edge, A. C. Fabian, Gary J. Ferland, B. R. Mcnamara, R. Mittal, J. B. R. Oonk, A. C. Quillen, H. R. Russell, J. S. Sanders, P. Salomé, G. M. Voit, R. J. Wilman, M. W. Wise
Physics and Astronomy Faculty Publications
We present new Chandra X-ray observations of the brightest cluster galaxy (BCG) in the cool-core cluster Abell 2597 (z= 0.0821). The data reveal an extensive kpc-scale X-ray cavity network as well as a 15-kpc filament of soft-excess gas exhibiting strong spatial correlation with archival Very Large Array radio data. In addition to several possible scenarios, multiwavelength evidence may suggest that the filament is associated with multiphase (103–107 K) gas that has been entrained and dredged-up by the propagating radio source. Stemming from a full spectral analysis, we also present profiles and 2D spectral maps of …
H2 Temperatures In The Crab Nebula, E. D. Loh, J. A. Baldwin, Gary J. Ferland, Z. K. Curtis, C. T. Richardson, A. C. Fabian, P. Salomé
H2 Temperatures In The Crab Nebula, E. D. Loh, J. A. Baldwin, Gary J. Ferland, Z. K. Curtis, C. T. Richardson, A. C. Fabian, P. Salomé
Physics and Astronomy Faculty Publications
We used K-band spectra to measure the H2 excitation temperatures in six molecular knots associated with the filaments in the Crab Nebula. The temperatures are quite high – in the range T∼ 2000–3000 K, just below the H2 dissociation temperature. This is the temperature range over which the H2 1–0 S(1) line at λ2.121 μm has its maximum emissivity per unit mass, so there may be many additional H2 cores with lower temperatures that are too faint to detect. We also measured the electron density in adjacent ionized gas, which on the assumption of …