Study of Outflows in Luminous Quasars at Redshift ∼0.4–0.8

Abstract

We perform a systematic study of outflow in the narrow-line region (NLR) of active galactic nuclei (AGNs) at z  ∼ 0.4–0.8 based upon a large sample of ∼900 quasars at z  ∼ 0.4–0.8. The sample is extracted from the Sloan Digital Sky Survey by mainly requiring that (1) the g-band magnitude is brighter than 19 mag and (2) the [O iii ] λ 5007 emission line has a signal-to-noise ratio larger than 30. Profiles of multiple emission lines are modeled by a sum of several Gaussian functions. The spectral analysis allows us to identify (1) a prevalence of both [O iii ] λ 5007 line blue asymmetry and bulk velocity blueshift of both [Ne iii ] λ 3869 and [Ne iii ] λ 3426 lines, when the [O ii ] λ 3727 line is used as a reference. The velocity offset of the [O iii ] λ 5007 line is, however, distributed around a value of zero, except for a few outliers. (2) Not only the significant [O iii ] λ 5007 line asymmetry, but also the large bulk velocity offsets of [Ne iii ] λ 3869 and [Ne v ] λ 3426 emission lines tend to occur in the objects with high L / L Edd , which is considerably consistent with the conclusions based on local AGNs. With three M BH estimation methods, the significance level of the trend is found to be better than 2.9 σ , 3.2 σ , and 1.8 σ for [O iii ], [Ne iii ], and [Ne v ], respectively. After excluding the role of radio jets, the revealed dependence of NLR gas outflow on L / L Edd allows us to argue that the pressure caused by the wind/radiation launched/emitted from a central supermassive black hole is the most likely origin of the outflow in these distant quasars, which implies that the outflow in luminous AGNs up to z  ∼ 1 have the same origin.