The Intermediate Line Region in AGN: a region "praeter necessitatem"?

As a consequence of improved S/N, spectral resolution and wavelength coverage various authors have introduced, without strong justification, new emitting regions to account for various emission line profile differences in AGN. The so-called CIVlambda1549 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 CIV and Balmer emission lines with different widths. The putative ILR component has often been included with the broad line profile in studies of CIV BLR properties. Failure to account for the composite nature of CIV emission, and for the presence of sometimes appreciable NLR CIV emission, has important consequences for our understanding of the BLR.Comment: 3 Figs. 1 Table, accepted for publication in Astrophysical Journal Letter

No Evidence for a Aystematic FEII Emission Line Redshift in Type 1 AGN

We test the recent claim by Hu et al. (2008) that FeII emission in Type 1 AGN shows a systematic redshift relative to the local source rest frame and broad-line Hbeta. We compile high s/n median composites using SDSS spectra from both the Hu et al. sample and our own sample of the 469 brightest DR5 spectra. Our composites are generated in bins of FWHM Hbeta and FeII strength as defined in our 4D Eigenvector 1 (4DE1) formalism. We find no evidence for a systematic FeII redshift and consistency with previous assumptions that FeII shift and width (FWHM) follow Hbeta shift and FWHM in virtually all sources. This result is consistent with the hypothesis that FeII emission (quasi-ubiquitous in type 1 sources) arises from a broad-line region with geometry and kinematics the same as that producing the Balmer lines.Comment: 12 pages, 1 table, 1 figure - accepted for publication in ApJ Letter