Inferences from a study of Fe II emission in radio-loud and radio-quiet quasars

From intermediate-resolution spectrophotometry of 33 quasars with redshift z < 0.7, significant statistical differences in the line properties emerge between the radio and radio-quiet objects. Fe II optical emission is rarer in radio quasars and less intense on average when present, whereas Fe II UV emission is always detected in both classes. Moreover, for the radio sample, Fe II optical emission is not correlated with the radio morphology, contrary to previous suggestions. Finally, in radio quasars the full-width at half maximum of Hβ and/or Mg II is statistically larger by nearly a factor of 2 than in radio-quiet ones. (author)