2006ApJ...648..158W

We analyze the physical properties of the poststarburst active galactic nucleus (AGN) SDSS J085338.27+033246.1 according to its optical spectrum and discuss its implications on AGNs' evolution. The spectra principal component analysis (PCA) method is developed to extract emission lines and absorption features from the total light spectrum. The emission-line analysis indicates that the object can be classified as a narrow-line Seyfert 1 galaxy with FeII/Hβ_B=2.4±0.2, large Eddington ratio (∼0.34), small black hole mass (∼1.1x10⁷ M_☉), and intermediately strong radio emission. A simple single stellar population model indicates that the absorption features are rather well reproduced by a ∼100 Myr old starburst with a mass of ∼7x10⁹ M_☉. However, the current star formation rate, ∼3.0 M_☉/yr, inferred from the [O II] emission is much smaller than the past average star formation rate, ∼70 M_☉/yr. The line ratio diagnosis using Baldwin-Phillips-Terlevich (BPT) diagrams indicates that the narrow emission lines are almost entirely emitted from H II regions. We further discuss a possible evolutionary path that links AGN and starburst phenomena.