English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

[Abridged] We present new VLT ISAAC spectra for 30 quasars, which we combinewith previous data to yield a sample of 53 intermediate redshift (z ~ 0.9 -3.0) sources. The sample is used to explore properties of prominent lines inthe Hbeta spectral region of these very luminous quasars. We find two majortrends: (1) a systematic increase of minimum FWHM Hbeta with luminosity(discussed in a previous paper). This lower FWHM envelope is best fit assumingthat the narrowest sources radiate near the Eddington limit, show line emissionfrom a virialized cloud distribution, and obey a well defined broad line regionsize vs. luminosity relation. (2) A systematic decrease of equivalent width of[OIII] (from W ~ 15 to ~ 1 A) with increasing source bolometric luminosity(from log L ~ 43 to log L ~ 49). Further identified trends requireddiscrimination between so-called Population A and B sources. We generate mediancomposite spectra in six luminosity bins Pop. A sources show reasonablysymmetric Lorentzian Hbeta profiles at all luminosities while Pop. B sourcesrequire two component fits involving an unshifted broad and a redshifted verybroad component. Very broad Hbeta increases in strength with increasing L whilethe broad component remains constant resulting in an apparent "Baldwin effect"with equivalent width decreasing from W ~ 80 to ~ 20 A over our sampleluminosity range. The roughly constant equivalent width shown by the Hbeta verybroad component implies production in optically-thick, photoionized gas. Theonset of the redshifted very broad component appears to be a critical changethat occurs near the Pop. A-B boundary at FWHM Hbeta ~ 4000 km/s which werelate to a critical Eddington ratio (~ 0.2 +/- 0.1).

VLT/ISAAC Spectra of the Hbeta Region in Intermediate-Redshift Quasars III. Hbeta Broad Line Profile Analysis and Inferences about BLR Structure