An Analysis of the Velocity Dependence of BLR Emission Line Ratios from HST and Optical Spectra

Details An Analysis of the Velocity Dependence of BLR Emission Line Ratios from HST and Optical Spectra An Analysis of the Velocity Dependence of BLR Emission Line Ratios from HST and Optical Spectra

Dec 1997

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997aas...191.2502s&link_type=abstract

American Astronomical Society, 191st AAS Meeting, #25.02; Bulletin of the American Astronomical Society, Vol. 29, p.1252

Astronomy and Astrophysics

Astronomy

Scientific paper

We present the results of a study of quasar emission line ratios as a function of projected velocity. Eight AGN with high S/N optical and UV spectra were analyzed with the intent of deducing the physical characteristics of the regions associated with high and low ionization emission lines as a function of velocity. The C III]/C IV/Lyalpha ratios show almost no velocity dependence. We compare the observed line ratios to predictions from photoionization models for the C III]/C IV and Lyalpha /C IV ratios. From these we establish values for the hydrogen density, n_H, and the ionization parameter, U, in the C(++) /C(+++) zones of the BLR cloud. We obtain typical values of n_H =~ 3 x 10(10) cm(-3) and U =~ 0.3 for solar abundance clouds. Our deduced n_H increases by almost an order of magnitude if we assume 5 Z_&sun; abundances. The deduced ionization parameter shows a slight decrease with increasing abundances. n_H and U show almost no velocity dependence. The conditions inferred from the C III]/C IV/Lyalpha ratios fail to reproduce the observed Balmer/Lyman profile ratios.

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