STIS Ultraviolet Spectral Evidence for Outflows in Extreme Narrow-Line Seyfert 1 Galaxies

Abstract

(abridged) I present and discuss the results of HST STIS observations of IRAS 13224-3809 and 1H 0707-495, two narrow-line Seyfert 1 (NLS1) galaxies. We discovered that high-ionization UV emission lines are much broader and strongly blueshifted compared with the low-ionization and intermediate-ionization lines, which are relatively narrow and centered at the rest wavelength. We interpret this as evidence that the high-ionization lines come from a wind, while the low-ionization lines are emitted from the accretion disk or low-velocity base of the wind. The optically thick disk blocks our view of the receding wind. We also found that not all NLS1s display strongly blueshifted emission lines, and the degree of asymmetry is inversely correlated with the equivalent width and correlated with the SiIII] to CIII] ratio, a density indicator. It may also be significant that these NLS1s display the extreme in the X-ray properties: they have the strongest X-ray soft-excess components and the highest-amplitude, flaring variability. We postulate that this combination of properties are all related to a high value of L/M_BH, even among NLS1s. The high-ionization and low-ionization lines are nearly completely kinematically separated, a fact that allows us to study the conditions in the disk and wind separately.(...)