ﻻ يوجد ملخص باللغة العربية
We present high S/N UV spectra for eight quasars at $zsim3$ obtained with VLT/FORS. The spectra enable us to analyze in detail the strongest emission features in the rest-frame range 1400-2000 AA of each source (ciii, siiii, aliii, siii, civ and siiv). Previous work indicates that a component of these lines is emitted in a region with well-defined properties i.e., a high density and low ionization emitting region). Flux ratios aliii/siiii, civ/aliii, siiv/siiii, civ/siiv and siii/siiii for this region permit us to strongly constrain electron density, ionization parameter and metallicity through the use of diagnostic maps built from {sc CLOUDY} simulations. Reliable estimates of the product density times ionization parameter allow us to derive the radius of the broad line region rb from the definition of the ionization parameter. The rb estimate and the assumption of virialized motions in the line emitting gas yields an estimate for black hole mass. We compare our results with estimates obtained from the rb -- luminosity correlation customarily employed to estimate black hole masses of high redshift quasars.
Black Hole Mass (M_BH) estimation in quasars, especially at high redshift, involves use of single epoch spectra with s/n and resolution that permit accurate measurement of the width of a broad line assumed to be a reliable virial estimator. Coupled w
We describe a method for determination of physical conditions in the broad line regions of a significant subsample of Seyfert-1 nuclei and quasars. Several diagnostic ratios based on intermediate (AlIII 1860, SiIII 1892) and high (CIV 1549, SiIV 1397
When an image of a strongly lensed quasar is microlensed, the different components of its spectrum are expected to be differentially magnified owing to the different sizes of the corresponding emitting region. Chromatic changes are expected to be obs
We have examined the physical conditions in the narrow-line region (NLR) of the Seyfert 2 galaxy Markarian 3, using long-slit spectra obtained with the Hubble Space Telescope/Space Telescope Imaging Spectrograph and photoionization models. We find th
A method is proposed for measuring the size of the broad emission line region (BLR) in quasars using broadband photometric data. A feasibility study, based on numerical simulations, points to the advantages and pitfalls associated with this approach.