The UV spectra of NLS1s - implications for their broad line regions

We study the UV spectra of NLS1 galaxies and compare them with typical Seyf ert 1 galaxies and quasars. The NLS1 spectra show narrower UV lines as well as weaker CIV lambda 1549 and CIII] lambda 1909 emission. We show that the se Line properties are due to a lower ionization parameter and somewhat hig her BLR cloud densities. These modified conditions can be explained by the hotter big blue bumps observed in NLS1s, which are in turn due to higher L/ L-Edd ratios, as shown by our accretion disk and corona modeling of the NLS 1 continua. We also present evidence that the Boroson and Green eigenvector 1, which is correlated with the optical and UV emission-line properties, i s not driven by orientation and hence NLS1s, which have extreme eigenvector 1 values, are not viewed from an extreme viewing angle. (C) 2000 Elsevier Science B.V. All rights reserved.