1999/04/15 by J. W. Sulentic, P. Marziani · 2 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/312060
3 Figs. 1 Table, accepted for publication in Astrophysical Journal Letters
arxiv created 1999/04/15 · openalex publication_date 1999/06/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
As a consequence of the improved signal-to-noise ratio, spectral resolution, and wavelength coverage, various authors have introduced, without strong justification, new emitting regions to account for various emission-line profile differences in active galactic nuclei. The so-called C IV λ1549 intermediate-line region (ILR) appears to be especially ill-defined. We present observational evidence that suggests the ILR is statistically indistinguishable from the classical narrow-line region (NLR). We present the results of theoretical models showing that a smooth density gradient in the NLR can produce C IV and Balmer emission lines with different widths. The putative ILR component has often been included with the broad line profile in studies of C IV broad-line region (BLR) properties. Failure to account for the composite nature of C IV emission, and for the presence of sometimes appreciable NLR C IV emission, has important consequences for our understanding of the BLR.