El cant de la sibyla

Pérez, Janet; Cremades, Ferran; Arlandis,

doi:10.2307/40140019

Cited by 1 publication

(1 citation statement)

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“…O'Brien, Goad, & Gondhalekar (1994) have combined photoionization and reverberation-mapping calculations in a way similar to the present study ( § 2.2). Their work, and also the one by Pérez, Robinson & de la Funte (1992), focused on the shape of the transfer function and the line responsivity in a few generic models. They did not attempt a detailed reconstruction of a specific data set, and the comparison with the observations includes only time lags, and not the detailed shape of the light curves.…”

Section: Motivation Choice Of Target and Previous Workmentioning

confidence: 99%

Modeling Variable Emission Lines in Active Galactic Nuclei: Method and Application to NGC 5548

Kaspi

Netzer

1999

ApJ

110

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We present a new scheme for modeling the broad line region in active galactic nuclei (AGNs). It involves photoionization calculations of a large number of clouds, in several pre-determined geometries, and a comparison of the calculated line intensities with observed emission line light curves. Fitting several observed light curves simultaneously provides strong constraints on model parameters such as the run of density and column density across the nucleus, the shape of the ionizing continuum, and the radial distribution of the emission line clouds.When applying the model to the Seyfert 1 galaxy NGC 5548, we were able to reconstruct the light curves of four ultraviolet emission-lines, in time and in absolute flux. This has not been achieved by any previous work. We argue that the Balmer lines light curves, and possibly also the Mg II λ2798 light curve, cannot be tested in this scheme because of the limitations of present-day photoionization codes. Our fit procedure can be used to rule out models where the particle density scales as r −2 , where r is the distance from the central source. The best models are those where the density scales as r −1 or r −1.5 . We can place a lower limit on the column density at a distance of 1 ld, of N col (r = 1) > ∼ 10 23 cm −2 and limit the particle density to be in the range of 10 12.5 > N(r = 1) > 10 11 cm −3 .We have also tested the idea that the spectral energy distribution (SED) of the ionizing continuum is changing with continuum luminosity. None of the variable-shape SED tried resulted in real improvement over a constant SED case although models with harder continuum during phases of higher luminosity seem to fit better the observed spectrum. Reddening and/or different composition seem to play a minor role, at least to the extent tested in this work.

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Section: Motivation Choice Of Target and Previous Workmentioning

confidence: 99%