An Atlas of Computed Equivalent Widths of Quasar Broad Emission Lines

Korista, K. T.; Baldwin, J. A.; Ferland, Gary J.; Verner, D. A.

doi:10.1086/312966

Cited by 222 publications

(361 citation statements)

References 33 publications

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“…A conclusive evidence for this scenario is provided by observations that find a high polarization level of the light at the bottom of the absorption troughs (Glenn, Schmidt & Foltz 1994;Cohen et al 1995;Ogle 1997;Schmidt & Hines 1999;Ogle et al 1999;Lamy & Hutsemékers 2000Brotherton, De Breuck & Schaefer 2006). The CF ≃ 0.2 − 0.3 required for the scattering medium is similar to the measured CF of 0.3 for the Broad Line Region (BLR; Korista et al 1997b;Maiolino et al 2001;Ruff et al 2012). Thus, it is likely that the BLR is the scattering medium Korista & Ferland 1998), if the BAL outflow resides at a distance comparable to that of the BLR.…”

Section: Discussionsupporting

confidence: 53%

On the origins of C iv absorption profile diversity in broad absorption line quasars

Baskin

Laor

Hamann

2015

Monthly Notices of the Royal Astronomical Society

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There is a large diversity in the C iv broad absorption line (BAL) profile among BAL quasars (BALQs). We quantify this diversity by exploring the distribution of the C iv BAL properties, FWHM, maximum depth of absorption and its velocity shift (v md ), using the SDSS DR7 quasar catalogue. We find the following: (i) Although the median C iv BAL profile in the quasar rest-frame becomes broader and shallower as the UV continuum slope (α UV at 1700-3000Å) gets bluer, the median individual profile in the absorber rest-frame remains identical, and is narrow (FWHM = 3500 km s −1 ) and deep. Only 4 per cent of BALs have FWHM > 10, 000 km s −1 . (ii) As the He ii emission equivalent-width (EW) decreases, the distributions of FWHM and v md extend to larger values, and the median maximum depth increases. These trends are consistent with theoretical models in which softer ionizing continua reduce overionization, and allow radiative acceleration of faster BAL outflows. (iii) As α UV becomes bluer, the distribution of v md extends to larger values. This trend may imply faster outflows at higher latitudes above the accretion disc plane. (iv) For non-BALQs, the C iv emission line decreases with decreasing He ii EW, and becomes more asymmetric and blueshifted. This suggests an increasing relative contribution of emission from the BAL outflow to the C iv emission line as the ionizing spectral energy distribution (SED) gets softer, which is consistent with the increasing fraction of BALQs as the ionizing SED gets softer.

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Section: Discussionsupporting

confidence: 53%

On the origins of C iv absorption profile diversity in broad absorption line quasars

Baskin

Laor

Hamann

2015

Monthly Notices of the Royal Astronomical Society

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“…It is an extension of the same model used in Bianchi et al (2010) and Marinucci et al (2011). The main ingredients are: plane parallel geometry, with the flux of photons striking the illuminated face of the cloud given in terms of ionization parameter U (Osterbrock & Ferland 2006); incident continuum modeled as in Korista et al (1997); constant electron density ne = 10 5 cm −3 ; elemental abundances as in Table 7.5 of cloudy documentation 1 ; grid parameters are log U = [1.00 : 4.00], step 0.25, log NH = [23.0 : 25.0], step 0.1, and AF e = [1.0 : 5.0]. Only the reflected spectrum, arising from the illuminated face of the cloud, has been taken into account in our model.…”

Section: Diffuse Highly-ionized Fe Emissionmentioning

confidence: 99%

Spatially resolved Fe K spectroscopy of NGC 4945

Marinucci

Bianchi

Fabbiano

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present the imaging and spectroscopic analysis of the combined Chandra ACIS-S observations of the Compton-thick Seyfert 2 galaxy NGC 4945. We performed a spatially-resolved spectroscopy of the circumnuclear environment of the source, picturing the innermost 200 parsecs around the highly absorbed nucleus. The additional 200 ks ACIS-S data with respect to the previous campaign allowed us to map with even greater detail the central structure of this source and to discover an enhanced iron emission in the innermost nuclear region, with respect to the associated Compton reflection continuum. We revealed that the Equivalent Width of the iron Kα line is spatially variable (ranging from 0.5 to 3 keV), on scales of tens of parsecs, likely due to the ionization state and orientation effects of the reprocessing material, with respect to the central X-ray illuminating source. A clump of highly ionized Fe xxv He-α is also detected, 40 parsecs east to the nucleus. When observations taken years apart are considered, the central unresolved reflected emission is found to remain constant.

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“…With this normalization the cloud size remains the same for all densities. This grid is similar to those given in Korista et al (1997), which contains further details.…”

Section: Emission-line Properties Of a Fractal Blr Cloud Distributionmentioning

confidence: 99%

Fractal Quasar Clouds

Bottorff

Ferland

2001

ApJ

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This paper examines whether a fractal cloud geometry can reproduce the emission-line spectra of active galactic nuclei (AGNs). The nature of the emitting clouds is unknown, but many current models invoke various types of magnetohydrodynamic conÐnement. Recent studies have argued that a fractal distribution of clouds, in which subsets of clouds occur in self-similar hierarchies, is a consequence of such conÐnement. Whatever the conÐnement mechanism, fractal cloud geometries are found in nature and may be present in AGNs too. We Ðrst outline how a fractal geometry can apply at the center of a luminous quasar. Scaling laws are derived that establish the number of hierarchies, typical sizes, column densities, and densities. Photoionization simulations are used to predict the integrated spectrum from the ensemble. Direct comparison with observations establishes all model parameters so that the Ðnal predictions are fully constrained. Theory suggests that denser clouds might form in regions of higher turbulence and that larger turbulence results in a wider dispersion of physical gas densities. An increase in turbulence is expected deeper within the gravitational potential of the black hole, resulting in a density gradient. We mimic this density gradient by employing two sets of clouds with identical fractal structuring but di †erent densities. The low-density clouds have a lower column density and large covering factor similar to the warm absorber. The high-density clouds have high column density and smaller covering factor similar to the broad-line region (BLR). A fractal geometry can simultaneously reproduce the covering factor, density, column density, BLR emission-line strengths, and BLR line ratios as inferred from observation. Absorption properties of the model are consistent with the integrated line-of-sight column density as determined from observations of X-ray absorption, and when scaled to a Seyfert galaxy, the model is consistent with the number of multiple UV absorption components observed in them. Rough estimates show that about one in 100 of the galaxies that harbor a supermassive black hole will show activity, assuming that material needs to be within its EUV continuum emitting radius for activity to occur. This is close to the observationally determined duty cycle. Stochastic feeding of the central engine of fractal cloud distribution of material may therefore account for continuum variations and long-term activity. The total cloud mass is much larger than that measured in ionized gas alone since the clouds are mutually self-shielding.

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An Atlas of Computed Equivalent Widths of Quasar Broad Emission Lines

Cited by 222 publications

References 33 publications

On the origins of C iv absorption profile diversity in broad absorption line quasars

On the origins of C iv absorption profile diversity in broad absorption line quasars

Spatially resolved Fe K spectroscopy of NGC 4945

Fractal Quasar Clouds

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