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Full-Text Articles in Physics
Nitrogen-To-Oxygen Abundance Ratio Variation In Quiescent Galaxies, Renbin Yan
Nitrogen-To-Oxygen Abundance Ratio Variation In Quiescent Galaxies, Renbin Yan
Physics and Astronomy Faculty Publications
For the first time, we establish a gas-phase abundance pattern calibration for quiescent galaxies using optical emission lines. Quiescent galaxies have warm ionized gas showing line ratios similar to low-ionization nuclear emission line regions. The ionization mechanism for the gas is still an unsettled puzzle. Despite the uncertainty in the ionization mechanism, we argue that we can still infer certain gas-phase abundance pattern from first principles. We show that the relative trend in N/O abundance can still be reliably measured based on [N II] λλ6548,6583/[O II] λλ3726,3729 and a direct measurement of the electron temperature. We construct a composite direct …
Shocks Or Photoionization: Direct Temperature Measurements Of The Low-Ionization Gas In Quiescent Galaxies, Renbin Yan
Shocks Or Photoionization: Direct Temperature Measurements Of The Low-Ionization Gas In Quiescent Galaxies, Renbin Yan
Physics and Astronomy Faculty Publications
The ionization mechanism of the low-ionization gas in quiescent red-sequence galaxies has been a long-standing puzzle. Direct temperature measurements would put strong constraints on this issue. We carefully selected a sample of quiescent red-sequence galaxies from Sloan Digital Sky Survey. We bin them into three bins with different [N II]/H α and [N II]/[O II] ratios, and we measure the temperature-sensitive [O III] λ4363, [N II] λ5755, [S II] λλ4068, 4076, and [O II] λλ7320, 7330 lines in the stacked spectra. The [S II] doublet ratios indicate the line-emitting gas is in the low-density regime (∼10–200 cm−3). We …
The Intermediate-Line Region In Active Galactic Nuclei, T. P. Adhikari, A. Różańska, B. Czerny, K. Hryniewicz, Gary J. Ferland
The Intermediate-Line Region In Active Galactic Nuclei, T. P. Adhikari, A. Różańska, B. Czerny, K. Hryniewicz, Gary J. Ferland
Physics and Astronomy Faculty Publications
We show that the recently observed suppression of the gap between the broad-line region (BLR) and the narrow-line region (NLR) in some active galactic nuclei (AGNs) can be fully explained by an increase of the gas density in the emitting region. Our model predicts the formation of the intermediate-line region (ILR) that is observed in some Seyfert galaxies by the detection of emission lines with intermediate-velocity FWHM ~ 700–1200 km s−1. These lines are believed to be originating from an ILR located somewhere between the BLR and NLR. As was previously proved, the apparent gap is assumed to …
Ultraviolet Emission Lines Of Si Ii In Quasars—Investigating The "Si Ii Disaster", Sibasish Laha, Francis P. Keenan, Gary J. Ferland, Catherine A. Ramsbottom, Kanti M. Aggarwal
Ultraviolet Emission Lines Of Si Ii In Quasars—Investigating The "Si Ii Disaster", Sibasish Laha, Francis P. Keenan, Gary J. Ferland, Catherine A. Ramsbottom, Kanti M. Aggarwal
Physics and Astronomy Faculty Publications
The observed line intensity ratios of the Si II λ1263 and λ1307 multiplets to that of Si II λ1814 in the broad-line region (BLR) of quasars are both an order of magnitude larger than the theoretical values. This was first pointed out by Baldwin et al., who termed it the "Si II disaster," and it has remained unresolved. We investigate the problem in the light of newly published atomic data for Si II. Specifically, we perform BLR calculations using several different atomic data sets within the CLOUDY modeling code under optically thick quasar cloud conditions. In addition, …
Disc Outflows And High-Luminosity True Type 2 Agn, Moshe Elitzur, Hagai Netzer
Disc Outflows And High-Luminosity True Type 2 Agn, Moshe Elitzur, Hagai Netzer
Physics and Astronomy Faculty Publications
The absence of intrinsic broad-line emission has been reported in a number of active galactic nuclei (AGN), including some with high Eddington ratios. Such ‘true type 2 AGN’ are inherent to the disc-wind scenario for the broad-line region: broad-line emission requires a minimal column density, implying a minimal outflow rate and thus a minimal accretion rate. Here we perform a detailed analysis of the consequences of mass conservation in the process of accretion through a central disc. The resulting constraints on luminosity are consistent with all the cases where claimed detections of true type 2 AGN pass stringent criteria, and …
Strong Variability Of The Coronal Line Region In Ngc 5548, Hermine Landt, Martin J. Ward, Katrien C. Steenbrugge, Gary J. Ferland
Strong Variability Of The Coronal Line Region In Ngc 5548, Hermine Landt, Martin J. Ward, Katrien C. Steenbrugge, Gary J. Ferland
Physics and Astronomy Faculty Publications
We present the second extensive study of the coronal line variability in an active galaxy. Our data set for the well-studied Seyfert galaxy NGC 5548 consists of five epochs of quasi-simultaneous optical and near-infrared spectroscopy spanning a period of about five years and three epochs of X-ray spectroscopy overlapping in time with it. Whereas the broad emission lines and hot dust emission varied only moderately, the coronal lines varied strongly. However, the observed high variability is mainly due to a flux decrease. Using the optical [Fe vii] and X-ray O vii emission lines we estimate that the coronal line gas …
Variability Of The Coronal Line Region In Ngc 4151, Hermine Landt, Martin J. Ward, Katrien C. Steenbrugge, Gary J. Ferland
Variability Of The Coronal Line Region In Ngc 4151, Hermine Landt, Martin J. Ward, Katrien C. Steenbrugge, Gary J. Ferland
Physics and Astronomy Faculty Publications
We present the first extensive study of the coronal line variability in an active galaxy. Our data set for the nearby source NGC 4151 consists of six epochs of quasi-simultaneous optical and near-infrared spectroscopy spanning a period of about 8 yr and five epochs of X-ray spectroscopy overlapping in time with it. None of the coronal lines showed the variability behaviour observed for the broad emission lines and hot dust emission. In general, the coronal lines varied only weakly, if at all. Using the optical [Fe vii] and X-ray O vii emission lines we estimate that the coronal line gas …
Atomic Data For Zn Ɪɪ: Improving Spectral Diagnostics Of Chemical Evolution In High-Redshift Galaxies, Romas Kisielius, Varsha P. Kulkarni, Gary J. Ferland, Pavel Bogdanovich, Debopam Som, Matt L. Lykins
Atomic Data For Zn Ɪɪ: Improving Spectral Diagnostics Of Chemical Evolution In High-Redshift Galaxies, Romas Kisielius, Varsha P. Kulkarni, Gary J. Ferland, Pavel Bogdanovich, Debopam Som, Matt L. Lykins
Physics and Astronomy Faculty Publications
Damped Lyα (DLA) and sub-DLA absorbers in quasar spectra provide the most sensitive tools for measuring the element abundances of distant galaxies. The estimation of abundances from absorption lines depends sensitively on the accuracy of the atomic data used. We have started a project to produce new atomic spectroscopic parameters for optical and UV spectral lines using state-of-the-art computer codes employing a very broad configuration interaction (CI) basis. Here we report our results for Zn ii, an ion used widely in studies of the interstellar medium (ISM) as well as DLAs and sub-DLAs. We report new calculations of many …
An Atlas Of Computed Equivalent Widths Of Quasar Broad Emission Lines, Kirk Korista, Jack Baldwin, Gary J. Ferland, Dima Verner
An Atlas Of Computed Equivalent Widths Of Quasar Broad Emission Lines, Kirk Korista, Jack Baldwin, Gary J. Ferland, Dima Verner
Physics and Astronomy Faculty Publications
We present graphically the results of several thousand photoionization calculations of broad emission-line clouds in quasars, spanning 7 orders of magnitude in hydrogen ionizing flux and particle density. The equivalent widths of 42 quasar emission lines are presented as contours in the particle density-ionizing flux plane for a typical incident continuum shape, solar chemical abundances, and cloud column density of N(H) = 1023 cm-2. Results are similarly given for a small subset of emission lines for two other column densities (1022 and 1024 cm-2), five other incident continuum shapes, and a gas …